diff options
Diffstat (limited to 'Documentation')
37 files changed, 1537 insertions, 402 deletions
diff --git a/Documentation/ABI/testing/sysfs-ata b/Documentation/ABI/testing/sysfs-ata new file mode 100644 index 000000000000..0a932155cbba --- /dev/null +++ b/Documentation/ABI/testing/sysfs-ata @@ -0,0 +1,99 @@ +What: /sys/class/ata_... +Date: August 2008 +Contact: Gwendal Grignou<gwendal@google.com> +Description: + +Provide a place in sysfs for storing the ATA topology of the system. This allows +retrieving various information about ATA objects. + +Files under /sys/class/ata_port +------------------------------- + + For each port, a directory ataX is created where X is the ata_port_id of + the port. The device parent is the ata host device. + +idle_irq (read) + + Number of IRQ received by the port while idle [some ata HBA only]. + +nr_pmp_links (read) + + If a SATA Port Multiplier (PM) is connected, number of link behind it. + +Files under /sys/class/ata_link +------------------------------- + + Behind each port, there is a ata_link. If there is a SATA PM in the + topology, 15 ata_link objects are created. + + If a link is behind a port, the directory name is linkX, where X is + ata_port_id of the port. + If a link is behind a PM, its name is linkX.Y where X is ata_port_id + of the parent port and Y the PM port. + +hw_sata_spd_limit + + Maximum speed supported by the connected SATA device. + +sata_spd_limit + + Maximum speed imposed by libata. + +sata_spd + + Current speed of the link [1.5, 3Gps,...]. + +Files under /sys/class/ata_device +--------------------------------- + + Behind each link, up to two ata device are created. + The name of the directory is devX[.Y].Z where: + - X is ata_port_id of the port where the device is connected, + - Y the port of the PM if any, and + - Z the device id: for PATA, there is usually 2 devices [0,1], + only 1 for SATA. + +class + Device class. Can be "ata" for disk, "atapi" for packet device, + "pmp" for PM, or "none" if no device was found behind the link. + +dma_mode + + Transfer modes supported by the device when in DMA mode. + Mostly used by PATA device. + +pio_mode + + Transfer modes supported by the device when in PIO mode. + Mostly used by PATA device. + +xfer_mode + + Current transfer mode. + +id + + Cached result of IDENTIFY command, as described in ATA8 7.16 and 7.17. + Only valid if the device is not a PM. + +gscr + + Cached result of the dump of PM GSCR register. + Valid registers are: + 0: SATA_PMP_GSCR_PROD_ID, + 1: SATA_PMP_GSCR_REV, + 2: SATA_PMP_GSCR_PORT_INFO, + 32: SATA_PMP_GSCR_ERROR, + 33: SATA_PMP_GSCR_ERROR_EN, + 64: SATA_PMP_GSCR_FEAT, + 96: SATA_PMP_GSCR_FEAT_EN, + 130: SATA_PMP_GSCR_SII_GPIO + Only valid if the device is a PM. + +spdn_cnt + + Number of time libata decided to lower the speed of link due to errors. + +ering + + Formatted output of the error ring of the device. diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power index 6123c523bfd7..7628cd1bc36a 100644 --- a/Documentation/ABI/testing/sysfs-devices-power +++ b/Documentation/ABI/testing/sysfs-devices-power @@ -77,3 +77,91 @@ Description: devices this attribute is set to "enabled" by bus type code or device drivers and in that cases it should be safe to leave the default value. + +What: /sys/devices/.../power/wakeup_count +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_count attribute contains the number + of signaled wakeup events associated with the device. This + attribute is read-only. If the device is not enabled to wake up + the system from sleep states, this attribute is empty. + +What: /sys/devices/.../power/wakeup_active_count +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_active_count attribute contains the + number of times the processing of wakeup events associated with + the device was completed (at the kernel level). This attribute + is read-only. If the device is not enabled to wake up the + system from sleep states, this attribute is empty. + +What: /sys/devices/.../power/wakeup_hit_count +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_hit_count attribute contains the + number of times the processing of a wakeup event associated with + the device might prevent the system from entering a sleep state. + This attribute is read-only. If the device is not enabled to + wake up the system from sleep states, this attribute is empty. + +What: /sys/devices/.../power/wakeup_active +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_active attribute contains either 1, + or 0, depending on whether or not a wakeup event associated with + the device is being processed (1). This attribute is read-only. + If the device is not enabled to wake up the system from sleep + states, this attribute is empty. + +What: /sys/devices/.../power/wakeup_total_time_ms +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_total_time_ms attribute contains + the total time of processing wakeup events associated with the + device, in milliseconds. This attribute is read-only. If the + device is not enabled to wake up the system from sleep states, + this attribute is empty. + +What: /sys/devices/.../power/wakeup_max_time_ms +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_max_time_ms attribute contains + the maximum time of processing a single wakeup event associated + with the device, in milliseconds. This attribute is read-only. + If the device is not enabled to wake up the system from sleep + states, this attribute is empty. + +What: /sys/devices/.../power/wakeup_last_time_ms +Date: September 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/devices/.../wakeup_last_time_ms attribute contains + the value of the monotonic clock corresponding to the time of + signaling the last wakeup event associated with the device, in + milliseconds. This attribute is read-only. If the device is + not enabled to wake up the system from sleep states, this + attribute is empty. + +What: /sys/devices/.../power/autosuspend_delay_ms +Date: September 2010 +Contact: Alan Stern <stern@rowland.harvard.edu> +Description: + The /sys/devices/.../power/autosuspend_delay_ms attribute + contains the autosuspend delay value (in milliseconds). Some + drivers do not want their device to suspend as soon as it + becomes idle at run time; they want the device to remain + inactive for a certain minimum period of time first. That + period is called the autosuspend delay. Negative values will + prevent the device from being suspended at run time (similar + to writing "on" to the power/control attribute). Values >= + 1000 will cause the autosuspend timer expiration to be rounded + up to the nearest second. + + Not all drivers support this attribute. If it isn't supported, + attempts to read or write it will yield I/O errors. diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module new file mode 100644 index 000000000000..cfcec3bffc0a --- /dev/null +++ b/Documentation/ABI/testing/sysfs-module @@ -0,0 +1,12 @@ +What: /sys/module/pch_phub/drivers/.../pch_mac +Date: August 2010 +KernelVersion: 2.6.35 +Contact: masa-korg@dsn.okisemi.com +Description: Write/read GbE MAC address. + +What: /sys/module/pch_phub/drivers/.../pch_firmware +Date: August 2010 +KernelVersion: 2.6.35 +Contact: masa-korg@dsn.okisemi.com +Description: Write/read Option ROM data. + diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power index 2875f1f74a07..194ca446ac28 100644 --- a/Documentation/ABI/testing/sysfs-power +++ b/Documentation/ABI/testing/sysfs-power @@ -99,9 +99,38 @@ Description: dmesg -s 1000000 | grep 'hash matches' + If you do not get any matches (or they appear to be false + positives), it is possible that the last PM event point + referred to a device created by a loadable kernel module. In + this case cat /sys/power/pm_trace_dev_match (see below) after + your system is started up and the kernel modules are loaded. + CAUTION: Using it will cause your machine's real-time (CMOS) clock to be set to a random invalid time after a resume. +What; /sys/power/pm_trace_dev_match +Date: October 2010 +Contact: James Hogan <james@albanarts.com> +Description: + The /sys/power/pm_trace_dev_match file contains the name of the + device associated with the last PM event point saved in the RTC + across reboots when pm_trace has been used. More precisely it + contains the list of current devices (including those + registered by loadable kernel modules since boot) which match + the device hash in the RTC at boot, with a newline after each + one. + + The advantage of this file over the hash matches printed to the + kernel log (see /sys/power/pm_trace), is that it includes + devices created after boot by loadable kernel modules. + + Due to the small hash size necessary to fit in the RTC, it is + possible that more than one device matches the hash, in which + case further investigation is required to determine which + device is causing the problem. Note that genuine RTC clock + values (such as when pm_trace has not been used), can still + match a device and output it's name here. + What: /sys/power/pm_async Date: January 2009 Contact: Rafael J. Wysocki <rjw@sisk.pl> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 910c923a9b86..2861055afd7a 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -136,6 +136,7 @@ #ifdef CONFIG_COMPAT .compat_ioctl = i915_compat_ioctl, #endif + .llseek = noop_llseek, }, .pci_driver = { .name = DRIVER_NAME, diff --git a/Documentation/DocBook/genericirq.tmpl b/Documentation/DocBook/genericirq.tmpl index 1448b33fd222..fb10fd08c05c 100644 --- a/Documentation/DocBook/genericirq.tmpl +++ b/Documentation/DocBook/genericirq.tmpl @@ -28,7 +28,7 @@ </authorgroup> <copyright> - <year>2005-2006</year> + <year>2005-2010</year> <holder>Thomas Gleixner</holder> </copyright> <copyright> @@ -100,6 +100,10 @@ <listitem><para>Edge type</para></listitem> <listitem><para>Simple type</para></listitem> </itemizedlist> + During the implementation we identified another type: + <itemizedlist> + <listitem><para>Fast EOI type</para></listitem> + </itemizedlist> In the SMP world of the __do_IRQ() super-handler another type was identified: <itemizedlist> @@ -153,6 +157,7 @@ is still available. This leads to a kind of duality for the time being. Over time the new model should be used in more and more architectures, as it enables smaller and cleaner IRQ subsystems. + It's deprecated for three years now and about to be removed. </para> </chapter> <chapter id="bugs"> @@ -217,6 +222,7 @@ <itemizedlist> <listitem><para>handle_level_irq</para></listitem> <listitem><para>handle_edge_irq</para></listitem> + <listitem><para>handle_fasteoi_irq</para></listitem> <listitem><para>handle_simple_irq</para></listitem> <listitem><para>handle_percpu_irq</para></listitem> </itemizedlist> @@ -233,33 +239,33 @@ are used by the default flow implementations. The following helper functions are implemented (simplified excerpt): <programlisting> -default_enable(irq) +default_enable(struct irq_data *data) { - desc->chip->unmask(irq); + desc->chip->irq_unmask(data); } -default_disable(irq) +default_disable(struct irq_data *data) { - if (!delay_disable(irq)) - desc->chip->mask(irq); + if (!delay_disable(data)) + desc->chip->irq_mask(data); } -default_ack(irq) +default_ack(struct irq_data *data) { - chip->ack(irq); + chip->irq_ack(data); } -default_mask_ack(irq) +default_mask_ack(struct irq_data *data) { - if (chip->mask_ack) { - chip->mask_ack(irq); + if (chip->irq_mask_ack) { + chip->irq_mask_ack(data); } else { - chip->mask(irq); - chip->ack(irq); + chip->irq_mask(data); + chip->irq_ack(data); } } -noop(irq) +noop(struct irq_data *data)) { } @@ -278,12 +284,27 @@ noop(irq) <para> The following control flow is implemented (simplified excerpt): <programlisting> -desc->chip->start(); +desc->chip->irq_mask(); handle_IRQ_event(desc->action); -desc->chip->end(); +desc->chip->irq_unmask(); </programlisting> </para> - </sect3> + </sect3> + <sect3 id="Default_FASTEOI_IRQ_flow_handler"> + <title>Default Fast EOI IRQ flow handler</title> + <para> + handle_fasteoi_irq provides a generic implementation + for interrupts, which only need an EOI at the end of + the handler + </para> + <para> + The following control flow is implemented (simplified excerpt): + <programlisting> +handle_IRQ_event(desc->action); +desc->chip->irq_eoi(); + </programlisting> + </para> + </sect3> <sect3 id="Default_Edge_IRQ_flow_handler"> <title>Default Edge IRQ flow handler</title> <para> @@ -294,20 +315,19 @@ desc->chip->end(); The following control flow is implemented (simplified excerpt): <programlisting> if (desc->status & running) { - desc->chip->hold(); + desc->chip->irq_mask(); desc->status |= pending | masked; return; } -desc->chip->start(); +desc->chip->irq_ack(); desc->status |= running; do { if (desc->status & masked) - desc->chip->enable(); + desc->chip->irq_unmask(); desc->status &= ~pending; handle_IRQ_event(desc->action); } while (status & pending); desc->status &= ~running; -desc->chip->end(); </programlisting> </para> </sect3> @@ -342,9 +362,9 @@ handle_IRQ_event(desc->action); <para> The following control flow is implemented (simplified excerpt): <programlisting> -desc->chip->start(); handle_IRQ_event(desc->action); -desc->chip->end(); +if (desc->chip->irq_eoi) + desc->chip->irq_eoi(); </programlisting> </para> </sect3> @@ -375,8 +395,7 @@ desc->chip->end(); mechanism. (It's necessary to enable CONFIG_HARDIRQS_SW_RESEND when you want to use the delayed interrupt disable feature and your hardware is not capable of retriggering an interrupt.) - The delayed interrupt disable can be runtime enabled, per interrupt, - by setting the IRQ_DELAYED_DISABLE flag in the irq_desc status field. + The delayed interrupt disable is not configurable. </para> </sect2> </sect1> @@ -387,13 +406,13 @@ desc->chip->end(); contains all the direct chip relevant functions, which can be utilized by the irq flow implementations. <itemizedlist> - <listitem><para>ack()</para></listitem> - <listitem><para>mask_ack() - Optional, recommended for performance</para></listitem> - <listitem><para>mask()</para></listitem> - <listitem><para>unmask()</para></listitem> - <listitem><para>retrigger() - Optional</para></listitem> - <listitem><para>set_type() - Optional</para></listitem> - <listitem><para>set_wake() - Optional</para></listitem> + <listitem><para>irq_ack()</para></listitem> + <listitem><para>irq_mask_ack() - Optional, recommended for performance</para></listitem> + <listitem><para>irq_mask()</para></listitem> + <listitem><para>irq_unmask()</para></listitem> + <listitem><para>irq_retrigger() - Optional</para></listitem> + <listitem><para>irq_set_type() - Optional</para></listitem> + <listitem><para>irq_set_wake() - Optional</para></listitem> </itemizedlist> These primitives are strictly intended to mean what they say: ack means ACK, masking means masking of an IRQ line, etc. It is up to the flow @@ -458,6 +477,7 @@ desc->chip->end(); <para> This chapter contains the autogenerated documentation of the internal functions. </para> +!Ikernel/irq/irqdesc.c !Ikernel/irq/handle.c !Ikernel/irq/chip.c </chapter> diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl index 6899f471fb15..6b4e07f28b69 100644 --- a/Documentation/DocBook/kernel-api.tmpl +++ b/Documentation/DocBook/kernel-api.tmpl @@ -257,7 +257,8 @@ X!Earch/x86/kernel/mca_32.c !Iblock/blk-sysfs.c !Eblock/blk-settings.c !Eblock/blk-exec.c -!Eblock/blk-barrier.c +!Eblock/blk-flush.c +!Eblock/blk-lib.c !Eblock/blk-tag.c !Iblock/blk-tag.c !Eblock/blk-integrity.c diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl index a0d479d1e1dd..f66f4df18690 100644 --- a/Documentation/DocBook/kernel-locking.tmpl +++ b/Documentation/DocBook/kernel-locking.tmpl @@ -1645,7 +1645,9 @@ the amount of locking which needs to be done. all the readers who were traversing the list when we deleted the element are finished. We use <function>call_rcu()</function> to register a callback which will actually destroy the object once - the readers are finished. + all pre-existing readers are finished. Alternatively, + <function>synchronize_rcu()</function> may be used to block until + all pre-existing are finished. </para> <para> But how does Read Copy Update know when the readers are @@ -1714,7 +1716,7 @@ the amount of locking which needs to be done. - object_put(obj); + list_del_rcu(&obj->list); cache_num--; -+ call_rcu(&obj->rcu, cache_delete_rcu, obj); ++ call_rcu(&obj->rcu, cache_delete_rcu); } /* Must be holding cache_lock */ @@ -1725,14 +1727,6 @@ the amount of locking which needs to be done. if (++cache_num > MAX_CACHE_SIZE) { struct object *i, *outcast = NULL; list_for_each_entry(i, &cache, list) { -@@ -85,6 +94,7 @@ - obj->popularity = 0; - atomic_set(&obj->refcnt, 1); /* The cache holds a reference */ - spin_lock_init(&obj->lock); -+ INIT_RCU_HEAD(&obj->rcu); - - spin_lock_irqsave(&cache_lock, flags); - __cache_add(obj); @@ -104,12 +114,11 @@ struct object *cache_find(int id) { diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index 790d1a812376..0c134f8afc6f 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -218,13 +218,22 @@ over a rather long period of time, but improvements are always welcome! include: a. Keeping a count of the number of data-structure elements - used by the RCU-protected data structure, including those - waiting for a grace period to elapse. Enforce a limit - on this number, stalling updates as needed to allow - previously deferred frees to complete. - - Alternatively, limit only the number awaiting deferred - free rather than the total number of elements. + used by the RCU-protected data structure, including + those waiting for a grace period to elapse. Enforce a + limit on this number, stalling updates as needed to allow + previously deferred frees to complete. Alternatively, + limit only the number awaiting deferred free rather than + the total number of elements. + + One way to stall the updates is to acquire the update-side + mutex. (Don't try this with a spinlock -- other CPUs + spinning on the lock could prevent the grace period + from ever ending.) Another way to stall the updates + is for the updates to use a wrapper function around + the memory allocator, so that this wrapper function + simulates OOM when there is too much memory awaiting an + RCU grace period. There are of course many other + variations on this theme. b. Limiting update rate. For example, if updates occur only once per hour, then no explicit rate limiting is required, @@ -365,3 +374,26 @@ over a rather long period of time, but improvements are always welcome! and the compiler to freely reorder code into and out of RCU read-side critical sections. It is the responsibility of the RCU update-side primitives to deal with this. + +17. Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and + the __rcu sparse checks to validate your RCU code. These + can help find problems as follows: + + CONFIG_PROVE_RCU: check that accesses to RCU-protected data + structures are carried out under the proper RCU + read-side critical section, while holding the right + combination of locks, or whatever other conditions + are appropriate. + + CONFIG_DEBUG_OBJECTS_RCU_HEAD: check that you don't pass the + same object to call_rcu() (or friends) before an RCU + grace period has elapsed since the last time that you + passed that same object to call_rcu() (or friends). + + __rcu sparse checks: tag the pointer to the RCU-protected data + structure with __rcu, and sparse will warn you if you + access that pointer without the services of one of the + variants of rcu_dereference(). + + These debugging aids can help you find problems that are + otherwise extremely difficult to spot. diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 44c6dcc93d6d..862c08ef1fde 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -80,6 +80,24 @@ o A CPU looping with bottom halves disabled. This condition can o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel without invoking schedule(). +o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might + happen to preempt a low-priority task in the middle of an RCU + read-side critical section. This is especially damaging if + that low-priority task is not permitted to run on any other CPU, + in which case the next RCU grace period can never complete, which + will eventually cause the system to run out of memory and hang. + While the system is in the process of running itself out of + memory, you might see stall-warning messages. + +o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that + is running at a higher priority than the RCU softirq threads. + This will prevent RCU callbacks from ever being invoked, + and in a CONFIG_TREE_PREEMPT_RCU kernel will further prevent + RCU grace periods from ever completing. Either way, the + system will eventually run out of memory and hang. In the + CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning + messages. + o A bug in the RCU implementation. o A hardware failure. This is quite unlikely, but has occurred diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index efd8cc95c06b..a851118775d8 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -125,6 +125,17 @@ o "b" is the batch limit for this CPU. If more than this number of RCU callbacks is ready to invoke, then the remainder will be deferred. +o "ci" is the number of RCU callbacks that have been invoked for + this CPU. Note that ci+ql is the number of callbacks that have + been registered in absence of CPU-hotplug activity. + +o "co" is the number of RCU callbacks that have been orphaned due to + this CPU going offline. + +o "ca" is the number of RCU callbacks that have been adopted due to + other CPUs going offline. Note that ci+co-ca+ql is the number of + RCU callbacks registered on this CPU. + There is also an rcu/rcudata.csv file with the same information in comma-separated-variable spreadsheet format. @@ -180,7 +191,7 @@ o "s" is the "signaled" state that drives force_quiescent_state()'s o "jfq" is the number of jiffies remaining for this grace period before force_quiescent_state() is invoked to help push things - along. Note that CPUs in dyntick-idle mode thoughout the grace + along. Note that CPUs in dyntick-idle mode throughout the grace period will not report on their own, but rather must be check by some other CPU via force_quiescent_state(). diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index 7f5fc3ba9c91..ecf7d04bca26 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX @@ -6,6 +6,8 @@ Interrupts - ARM Interrupt subsystem documentation IXP2000 - Release Notes for Linux on Intel's IXP2000 Network Processor +msm + - MSM specific documentation Netwinder - Netwinder specific documentation Porting diff --git a/Documentation/arm/msm/gpiomux.txt b/Documentation/arm/msm/gpiomux.txt new file mode 100644 index 000000000000..67a81620adf6 --- /dev/null +++ b/Documentation/arm/msm/gpiomux.txt @@ -0,0 +1,176 @@ +This document provides an overview of the msm_gpiomux interface, which +is used to provide gpio pin multiplexing and configuration on mach-msm +targets. + +History +======= + +The first-generation API for gpio configuration & multiplexing on msm +is the function gpio_tlmm_config(). This function has a few notable +shortcomings, which led to its deprecation and replacement by gpiomux: + +The 'disable' parameter: Setting the second parameter to +gpio_tlmm_config to GPIO_CFG_DISABLE tells the peripheral +processor in charge of the subsystem to perform a look-up into a +low-power table and apply the low-power/sleep setting for the pin. +As the msm family evolved this became problematic. Not all pins +have sleep settings, not all peripheral processors will accept requests +to apply said sleep settings, and not all msm targets have their gpio +subsystems managed by a peripheral processor. In order to get consistent +behavior on all targets, drivers are forced to ignore this parameter, +rendering it useless. + +The 'direction' flag: for all mux-settings other than raw-gpio (0), +the output-enable bit of a gpio is hard-wired to a known +input (usually VDD or ground). For those settings, the direction flag +is meaningless at best, and deceptive at worst. In addition, using the +direction flag to change output-enable (OE) directly can cause trouble in +gpiolib, which has no visibility into gpio direction changes made +in this way. Direction control in gpio mode should be made through gpiolib. + +Key Features of gpiomux +======================= + +- A consistent interface across all generations of msm. Drivers can expect +the same results on every target. +- gpiomux plays nicely with gpiolib. Functions that should belong to gpiolib +are left to gpiolib and not duplicated here. gpiomux is written with the +intent that gpio_chips will call gpiomux reference-counting methods +from their request() and free() hooks, providing full integration. +- Tabular configuration. Instead of having to call gpio_tlmm_config +hundreds of times, gpio configuration is placed in a single table. +- Per-gpio sleep. Each gpio is individually reference counted, allowing only +those lines which are in use to be put in high-power states. +- 0 means 'do nothing': all flags are designed so that the default memset-zero +equates to a sensible default of 'no configuration', preventing users +from having to provide hundreds of 'no-op' configs for unused or +unwanted lines. + +Usage +===== + +To use gpiomux, provide configuration information for relevant gpio lines +in the msm_gpiomux_configs table. Since a 0 equates to "unconfigured", +only those lines to be managed by gpiomux need to be specified. Here +is a completely fictional example: + +struct msm_gpiomux_config msm_gpiomux_configs[GPIOMUX_NGPIOS] = { + [12] = { + .active = GPIOMUX_VALID | GPIOMUX_DRV_8MA | GPIOMUX_FUNC_1, + .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, + }, + [34] = { + .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, + }, +}; + +To indicate that a gpio is in use, call msm_gpiomux_get() to increase +its reference count. To decrease the reference count, call msm_gpiomux_put(). + +The effect of this configuration is as follows: + +When the system boots, gpios 12 and 34 will be initialized with their +'suspended' configurations. All other gpios, which were left unconfigured, +will not be touched. + +When msm_gpiomux_get() is called on gpio 12 to raise its reference count +above 0, its active configuration will be applied. Since no other gpio +line has a valid active configuration, msm_gpiomux_get() will have no +effect on any other line. + +When msm_gpiomux_put() is called on gpio 12 or 34 to drop their reference +count to 0, their suspended configurations will be applied. +Since no other gpio line has a valid suspended configuration, no other +gpio line will be effected by msm_gpiomux_put(). Since gpio 34 has no valid +active configuration, this is effectively a no-op for gpio 34 as well, +with one small caveat, see the section "About Output-Enable Settings". + +All of the GPIOMUX_VALID flags may seem like unnecessary overhead, but +they address some important issues. As unused entries (all those +except 12 and 34) are zero-filled, gpiomux needs a way to distinguish +the used fields from the unused. In addition, the all-zero pattern +is a valid configuration! Therefore, gpiomux defines an additional bit +which is used to indicate when a field is used. This has the pleasant +side-effect of allowing calls to msm_gpiomux_write to use '0' to indicate +that a value should not be changed: + + msm_gpiomux_write(0, GPIOMUX_VALID, 0); + +replaces the active configuration of gpio 0 with an all-zero configuration, +but leaves the suspended configuration as it was. + +Static Configurations +===================== + +To install a static configuration, which is applied at boot and does +not change after that, install a configuration with a suspended component +but no active component, as in the previous example: + + [34] = { + .suspended = GPIOMUX_VALID | GPIOMUX_PULL_DOWN, + }, + +The suspended setting is applied during boot, and the lack of any valid +active setting prevents any other setting from being applied at runtime. +If other subsystems attempting to access the line is a concern, one could +*really* anchor the configuration down by calling msm_gpiomux_get on the +line at initialization to move the line into active mode. With the line +held, it will never be re-suspended, and with no valid active configuration, +no new configurations will be applied. + +But then, if having other subsystems grabbing for the line is truly a concern, +it should be reserved with gpio_request instead, which carries an implicit +msm_gpiomux_get. + +gpiomux and gpiolib +=================== + +It is expected that msm gpio_chips will call msm_gpiomux_get() and +msm_gpiomux_put() from their request and free hooks, like this fictional +example: + +static int request(struct gpio_chip *chip, unsigned offset) +{ + return msm_gpiomux_get(chip->base + offset); +} + +static void free(struct gpio_chip *chip, unsigned offset) +{ + msm_gpiomux_put(chip->base + offset); +} + + ...somewhere in a gpio_chip declaration... + .request = request, + .free = free, + +This provides important functionality: +- It guarantees that a gpio line will have its 'active' config applied + when the line is requested, and will not be suspended while the line + remains requested; and +- It guarantees that gpio-direction settings from gpiolib behave sensibly. + See "About Output-Enable Settings." + +This mechanism allows for "auto-request" of gpiomux lines via gpiolib +when it is suitable. Drivers wishing more exact control are, of course, +free to also use msm_gpiomux_set and msm_gpiomux_get. + +About Output-Enable Settings +============================ + +Some msm targets do not have the ability to query the current gpio +configuration setting. This means that changes made to the output-enable +(OE) bit by gpiolib cannot be consistently detected and preserved by gpiomux. +Therefore, when gpiomux applies a configuration setting, any direction +settings which may have been applied by gpiolib are lost and the default +input settings are re-applied. + +For this reason, drivers should not assume that gpio direction settings +continue to hold if they free and then re-request a gpio. This seems like +common sense - after all, anybody could have obtained the line in the +meantime - but it needs saying. + +This also means that calls to msm_gpiomux_write will reset the OE bit, +which means that if the gpio line is held by a client of gpiolib and +msm_gpiomux_write is called, the direction setting has been lost and +gpiolib's internal state has been broken. +Release gpio lines before reconfiguring them. diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX index a406286f6f3e..d111e3b23db0 100644 --- a/Documentation/block/00-INDEX +++ b/Documentation/block/00-INDEX @@ -1,7 +1,5 @@ 00-INDEX - This file -barrier.txt - - I/O Barriers biodoc.txt - Notes on the Generic Block Layer Rewrite in Linux 2.5 capability.txt @@ -16,3 +14,5 @@ stat.txt - Block layer statistics in /sys/block/<dev>/stat switching-sched.txt - Switching I/O schedulers at runtime +writeback_cache_control.txt + - Control of volatile write back caches diff --git a/Documentation/block/barrier.txt b/Documentation/block/barrier.txt deleted file mode 100644 index 2c2f24f634e4..000000000000 --- a/Documentation/block/barrier.txt +++ /dev/null @@ -1,261 +0,0 @@ -I/O Barriers -============ -Tejun Heo <htejun@gmail.com>, July 22 2005 - -I/O barrier requests are used to guarantee ordering around the barrier -requests. Unless you're crazy enough to use disk drives for -implementing synchronization constructs (wow, sounds interesting...), -the ordering is meaningful only for write requests for things like -journal checkpoints. All requests queued before a barrier request -must be finished (made it to the physical medium) before the barrier -request is started, and all requests queued after the barrier request -must be started only after the barrier request is finished (again, -made it to the physical medium). - -In other words, I/O barrier requests have the following two properties. - -1. Request ordering - -Requests cannot pass the barrier request. Preceding requests are -processed before the barrier and following requests after. - -Depending on what features a drive supports, this can be done in one -of the following three ways. - -i. For devices which have queue depth greater than 1 (TCQ devices) and -support ordered tags, block layer can just issue the barrier as an -ordered request and the lower level driver, controller and drive -itself are responsible for making sure that the ordering constraint is -met. Most modern SCSI controllers/drives should support this. - -NOTE: SCSI ordered tag isn't currently used due to limitation in the - SCSI midlayer, see the following random notes section. - -ii. For devices which have queue depth greater than 1 but don't -support ordered tags, block layer ensures that the requests preceding -a barrier request finishes before issuing the barrier request. Also, -it defers requests following the barrier until the barrier request is -finished. Older SCSI controllers/drives and SATA drives fall in this -category. - -iii. Devices which have queue depth of 1. This is a degenerate case -of ii. Just keeping issue order suffices. Ancient SCSI -controllers/drives and IDE drives are in this category. - -2. Forced flushing to physical medium - -Again, if you're not gonna do synchronization with disk drives (dang, -it sounds even more appealing now!), the reason you use I/O barriers -is mainly to protect filesystem integrity when power failure or some -other events abruptly stop the drive from operating and possibly make -the drive lose data in its cache. So, I/O barriers need to guarantee -that requests actually get written to non-volatile medium in order. - -There are four cases, - -i. No write-back cache. Keeping requests ordered is enough. - -ii. Write-back cache but no flush operation. There's no way to -guarantee physical-medium commit order. This kind of devices can't to -I/O barriers. - -iii. Write-back cache and flush operation but no FUA (forced unit -access). We need two cache flushes - before and after the barrier -request. - -iv. Write-back cache, flush operation and FUA. We still need one -flush to make sure requests preceding a barrier are written to medium, -but post-barrier flush can be avoided by using FUA write on the -barrier itself. - - -How to support barrier requests in drivers ------------------------------------------- - -All barrier handling is done inside block layer proper. All low level -drivers have to are implementing its prepare_flush_fn and using one -the following two functions to indicate what barrier type it supports -and how to prepare flush requests. Note that the term 'ordered' is -used to indicate the whole sequence of performing barrier requests -including draining and flushing. - -typedef void (prepare_flush_fn)(struct request_queue *q, struct request *rq); - -int blk_queue_ordered(struct request_queue *q, unsigned ordered, - prepare_flush_fn *prepare_flush_fn); - -@q : the queue in question -@ordered : the ordered mode the driver/device supports -@prepare_flush_fn : this function should prepare @rq such that it - flushes cache to physical medium when executed - -For example, SCSI disk driver's prepare_flush_fn looks like the -following. - -static void sd_prepare_flush(struct request_queue *q, struct request *rq) -{ - memset(rq->cmd, 0, sizeof(rq->cmd)); - rq->cmd_type = REQ_TYPE_BLOCK_PC; - rq->timeout = SD_TIMEOUT; - rq->cmd[0] = SYNCHRONIZE_CACHE; - rq->cmd_len = 10; -} - -The following seven ordered modes are supported. The following table -shows which mode should be used depending on what features a -device/driver supports. In the leftmost column of table, -QUEUE_ORDERED_ prefix is omitted from the mode names to save space. - -The table is followed by description of each mode. Note that in the -descriptions of QUEUE_ORDERED_DRAIN*, '=>' is used whereas '->' is -used for QUEUE_ORDERED_TAG* descriptions. '=>' indicates that the -preceding step must be complete before proceeding to the next step. -'->' indicates that the next step can start as soon as the previous -step is issued. - - write-back cache ordered tag flush FUA ------------------------------------------------------------------------ -NONE yes/no N/A no N/A -DRAIN no no N/A N/A -DRAIN_FLUSH yes no yes no -DRAIN_FUA yes no yes yes -TAG no yes N/A N/A -TAG_FLUSH yes yes yes no -TAG_FUA yes yes yes yes - - -QUEUE_ORDERED_NONE - I/O barriers are not needed and/or supported. - - Sequence: N/A - -QUEUE_ORDERED_DRAIN - Requests are ordered by draining the request queue and cache - flushing isn't needed. - - Sequence: drain => barrier - -QUEUE_ORDERED_DRAIN_FLUSH - Requests are ordered by draining the request queue and both - pre-barrier and post-barrier cache flushings are needed. - - Sequence: drain => preflush => barrier => postflush - -QUEUE_ORDERED_DRAIN_FUA - Requests are ordered by draining the request queue and - pre-barrier cache flushing is needed. By using FUA on barrier - request, post-barrier flushing can be skipped. - - Sequence: drain => preflush => barrier - -QUEUE_ORDERED_TAG - Requests are ordered by ordered tag and cache flushing isn't - needed. - - Sequence: barrier - -QUEUE_ORDERED_TAG_FLUSH - Requests are ordered by ordered tag and both pre-barrier and - post-barrier cache flushings are needed. - - Sequence: preflush -> barrier -> postflush - -QUEUE_ORDERED_TAG_FUA - Requests are ordered by ordered tag and pre-barrier cache - flushing is needed. By using FUA on barrier request, - post-barrier flushing can be skipped. - - Sequence: preflush -> barrier - - -Random notes/caveats --------------------- - -* SCSI layer currently can't use TAG ordering even if the drive, -controller and driver support it. The problem is that SCSI midlayer -request dispatch function is not atomic. It releases queue lock and -switch to SCSI host lock during issue and it's possible and likely to -happen in time that requests change their relative positions. Once -this problem is solved, TAG ordering can be enabled. - -* Currently, no matter which ordered mode is used, there can be only -one barrier request in progress. All I/O barriers are held off by -block layer until the previous I/O barrier is complete. This doesn't -make any difference for DRAIN ordered devices, but, for TAG ordered -devices with very high command latency, passing multiple I/O barriers -to low level *might* be helpful if they are very frequent. Well, this -certainly is a non-issue. I'm writing this just to make clear that no -two I/O barrier is ever passed to low-level driver. - -* Completion order. Requests in ordered sequence are issued in order -but not required to finish in order. Barrier implementation can -handle out-of-order completion of ordered sequence. IOW, the requests -MUST be processed in order but the hardware/software completion paths -are allowed to reorder completion notifications - eg. current SCSI -midlayer doesn't preserve completion order during error handling. - -* Requeueing order. Low-level drivers are free to requeue any request -after they removed it from the request queue with -blkdev_dequeue_request(). As barrier sequence should be kept in order -when requeued, generic elevator code takes care of putting requests in -order around barrier. See blk_ordered_req_seq() and -ELEVATOR_INSERT_REQUEUE handling in __elv_add_request() for details. - -Note that block drivers must not requeue preceding requests while -completing latter requests in an ordered sequence. Currently, no -error checking is done against this. - -* Error handling. Currently, block layer will report error to upper -layer if any of requests in an ordered sequence fails. Unfortunately, -this doesn't seem to be enough. Look at the following request flow. -QUEUE_ORDERED_TAG_FLUSH is in use. - - [0] [1] [2] [3] [pre] [barrier] [post] < [4] [5] [6] ... > - still in elevator - -Let's say request [2], [3] are write requests to update file system -metadata (journal or whatever) and [barrier] is used to mark that -those updates are valid. Consider the following sequence. - - i. Requests [0] ~ [post] leaves the request queue and enters - low-level driver. - ii. After a while, unfortunately, something goes wrong and the - drive fails [2]. Note that any of [0], [1] and [3] could have - completed by this time, but [pre] couldn't have been finished - as the drive must process it in order and it failed before - processing that command. - iii. Error handling kicks in and determines that the error is - unrecoverable and fails [2], and resumes operation. - iv. [pre] [barrier] [post] gets processed. - v. *BOOM* power fails - -The problem here is that the barrier request is *supposed* to indicate -that filesystem update requests [2] and [3] made it safely to the -physical medium and, if the machine crashes after the barrier is -written, filesystem recovery code can depend on that. Sadly, that -isn't true in this case anymore. IOW, the success of a I/O barrier -should also be dependent on success of some of the preceding requests, -where only upper layer (filesystem) knows what 'some' is. - -This can be solved by implementing a way to tell the block layer which -requests affect the success of the following barrier request and -making lower lever drivers to resume operation on error only after -block layer tells it to do so. - -As the probability of this happening is very low and the drive should -be faulty, implementing the fix is probably an overkill. But, still, -it's there. - -* In previous drafts of barrier implementation, there was fallback -mechanism such that, if FUA or ordered TAG fails, less fancy ordered -mode can be selected and the failed barrier request is retried -automatically. The rationale for this feature was that as FUA is -pretty new in ATA world and ordered tag was never used widely, there -could be devices which report to support those features but choke when -actually given such requests. - - This was removed for two reasons 1. it's an overkill 2. it's -impossible to implement properly when TAG ordering is used as low -level drivers resume after an error automatically. If it's ever -needed adding it back and modifying low level drivers accordingly -shouldn't be difficult. diff --git a/Documentation/block/writeback_cache_control.txt b/Documentation/block/writeback_cache_control.txt new file mode 100644 index 000000000000..83407d36630a --- /dev/null +++ b/Documentation/block/writeback_cache_control.txt @@ -0,0 +1,86 @@ + +Explicit volatile write back cache control +===================================== + +Introduction +------------ + +Many storage devices, especially in the consumer market, come with volatile +write back caches. That means the devices signal I/O completion to the +operating system before data actually has hit the non-volatile storage. This +behavior obviously speeds up various workloads, but it means the operating +system needs to force data out to the non-volatile storage when it performs +a data integrity operation like fsync, sync or an unmount. + +The Linux block layer provides two simple mechanisms that let filesystems +control the caching behavior of the storage device. These mechanisms are +a forced cache flush, and the Force Unit Access (FUA) flag for requests. + + +Explicit cache flushes +---------------------- + +The REQ_FLUSH flag can be OR ed into the r/w flags of a bio submitted from +the filesystem and will make sure the volatile cache of the storage device +has been flushed before the actual I/O operation is started. This explicitly +guarantees that previously completed write requests are on non-volatile +storage before the flagged bio starts. In addition the REQ_FLUSH flag can be +set on an otherwise empty bio structure, which causes only an explicit cache +flush without any dependent I/O. It is recommend to use +the blkdev_issue_flush() helper for a pure cache flush. + + +Forced Unit Access +----------------- + +The REQ_FUA flag can be OR ed into the r/w flags of a bio submitted from the +filesystem and will make sure that I/O completion for this request is only +signaled after the data has been committed to non-volatile storage. + + +Implementation details for filesystems +-------------------------------------- + +Filesystems can simply set the REQ_FLUSH and REQ_FUA bits and do not have to +worry if the underlying devices need any explicit cache flushing and how +the Forced Unit Access is implemented. The REQ_FLUSH and REQ_FUA flags +may both be set on a single bio. + + +Implementation details for make_request_fn based block drivers +-------------------------------------------------------------- + +These drivers will always see the REQ_FLUSH and REQ_FUA bits as they sit +directly below the submit_bio interface. For remapping drivers the REQ_FUA +bits need to be propagated to underlying devices, and a global flush needs +to be implemented for bios with the REQ_FLUSH bit set. For real device +drivers that do not have a volatile cache the REQ_FLUSH and REQ_FUA bits +on non-empty bios can simply be ignored, and REQ_FLUSH requests without +data can be completed successfully without doing any work. Drivers for +devices with volatile caches need to implement the support for these +flags themselves without any help from the block layer. + + +Implementation details for request_fn based block drivers +-------------------------------------------------------------- + +For devices that do not support volatile write caches there is no driver +support required, the block layer completes empty REQ_FLUSH requests before +entering the driver and strips off the REQ_FLUSH and REQ_FUA bits from +requests that have a payload. For devices with volatile write caches the +driver needs to tell the block layer that it supports flushing caches by +doing: + + blk_queue_flush(sdkp->disk->queue, REQ_FLUSH); + +and handle empty REQ_FLUSH requests in its prep_fn/request_fn. Note that +REQ_FLUSH requests with a payload are automatically turned into a sequence +of an empty REQ_FLUSH request followed by the actual write by the block +layer. For devices that also support the FUA bit the block layer needs +to be told to pass through the REQ_FUA bit using: + + blk_queue_flush(sdkp->disk->queue, REQ_FLUSH | REQ_FUA); + +and the driver must handle write requests that have the REQ_FUA bit set +in prep_fn/request_fn. If the FUA bit is not natively supported the block +layer turns it into an empty REQ_FLUSH request after the actual write. diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt index 6919d62591d9..d6da611f8f63 100644 --- a/Documentation/cgroups/blkio-controller.txt +++ b/Documentation/cgroups/blkio-controller.txt @@ -8,12 +8,17 @@ both at leaf nodes as well as at intermediate nodes in a storage hierarchy. Plan is to use the same cgroup based management interface for blkio controller and based on user options switch IO policies in the background. -In the first phase, this patchset implements proportional weight time based -division of disk policy. It is implemented in CFQ. Hence this policy takes -effect only on leaf nodes when CFQ is being used. +Currently two IO control policies are implemented. First one is proportional +weight time based division of disk policy. It is implemented in CFQ. Hence +this policy takes effect only on leaf nodes when CFQ is being used. The second +one is throttling policy which can be used to specify upper IO rate limits +on devices. This policy is implemented in generic block layer and can be +used on leaf nodes as well as higher level logical devices like device mapper. HOWTO ===== +Proportional Weight division of bandwidth +----------------------------------------- You can do a very simple testing of running two dd threads in two different cgroups. Here is what you can do. @@ -55,6 +60,35 @@ cgroups. Here is what you can do. group dispatched to the disk. We provide fairness in terms of disk time, so ideally io.disk_time of cgroups should be in proportion to the weight. +Throttling/Upper Limit policy +----------------------------- +- Enable Block IO controller + CONFIG_BLK_CGROUP=y + +- Enable throttling in block layer + CONFIG_BLK_DEV_THROTTLING=y + +- Mount blkio controller + mount -t cgroup -o blkio none /cgroup/blkio + +- Specify a bandwidth rate on particular device for root group. The format + for policy is "<major>:<minor> <byes_per_second>". + + echo "8:16 1048576" > /cgroup/blkio/blkio.read_bps_device + + Above will put a limit of 1MB/second on reads happening for root group + on device having major/minor number 8:16. + +- Run dd to read a file and see if rate is throttled to 1MB/s or not. + + # dd if=/mnt/common/zerofile of=/dev/null bs=4K count=1024 + # iflag=direct + 1024+0 records in + 1024+0 records out + 4194304 bytes (4.2 MB) copied, 4.0001 s, 1.0 MB/s + + Limits for writes can be put using blkio.write_bps_device file. + Various user visible config options =================================== CONFIG_BLK_CGROUP @@ -68,8 +102,13 @@ CONFIG_CFQ_GROUP_IOSCHED - Enables group scheduling in CFQ. Currently only 1 level of group creation is allowed. +CONFIG_BLK_DEV_THROTTLING + - Enable block device throttling support in block layer. + Details of cgroup files ======================= +Proportional weight policy files +-------------------------------- - blkio.weight - Specifies per cgroup weight. This is default weight of the group on all the devices until and unless overridden by per device rule. @@ -210,6 +249,67 @@ Details of cgroup files and minor number of the device and third field specifies the number of times a group was dequeued from a particular device. +Throttling/Upper limit policy files +----------------------------------- +- blkio.throttle.read_bps_device + - Specifies upper limit on READ rate from the device. IO rate is + specified in bytes per second. Rules are per deivce. Following is + the format. + + echo "<major>:<minor> <rate_bytes_per_second>" > /cgrp/blkio.read_bps_device + +- blkio.throttle.write_bps_device + - Specifies upper limit on WRITE rate to the device. IO rate is + specified in bytes per second. Rules are per deivce. Following is + the format. + + echo "<major>:<minor> <rate_bytes_per_second>" > /cgrp/blkio.write_bps_device + +- blkio.throttle.read_iops_device + - Specifies upper limit on READ rate from the device. IO rate is + specified in IO per second. Rules are per deivce. Following is + the format. + + echo "<major>:<minor> <rate_io_per_second>" > /cgrp/blkio.read_iops_device + +- blkio.throttle.write_iops_device + - Specifies upper limit on WRITE rate to the device. IO rate is + specified in io per second. Rules are per deivce. Following is + the format. + + echo "<major>:<minor> <rate_io_per_second>" > /cgrp/blkio.write_iops_device + +Note: If both BW and IOPS rules are specified for a device, then IO is + subjectd to both the constraints. + +- blkio.throttle.io_serviced + - Number of IOs (bio) completed to/from the disk by the group (as + seen by throttling policy). These are further divided by the type + of operation - read or write, sync or async. First two fields specify + the major and minor number of the device, third field specifies the + operation type and the fourth field specifies the number of IOs. + + blkio.io_serviced does accounting as seen by CFQ and counts are in + number of requests (struct request). On the other hand, + blkio.throttle.io_serviced counts number of IO in terms of number + of bios as seen by throttling policy. These bios can later be + merged by elevator and total number of requests completed can be + lesser. + +- blkio.throttle.io_service_bytes + - Number of bytes transferred to/from the disk by the group. These + are further divided by the type of operation - read or write, sync + or async. First two fields specify the major and minor number of the + device, third field specifies the operation type and the fourth field + specifies the number of bytes. + + These numbers should roughly be same as blkio.io_service_bytes as + updated by CFQ. The difference between two is that + blkio.io_service_bytes will not be updated if CFQ is not operating + on request queue. + +Common files among various policies +----------------------------------- - blkio.reset_stats - Writing an int to this file will result in resetting all the stats for that cgroup. diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt index f1c5c4bccd3e..902d3151f527 100644 --- a/Documentation/cputopology.txt +++ b/Documentation/cputopology.txt @@ -14,25 +14,39 @@ to /proc/cpuinfo. identifier (rather than the kernel's). The actual value is architecture and platform dependent. -3) /sys/devices/system/cpu/cpuX/topology/thread_siblings: +3) /sys/devices/system/cpu/cpuX/topology/book_id: + + the book ID of cpuX. Typically it is the hardware platform's + identifier (rather than the kernel's). The actual value is + architecture and platform dependent. + +4) /sys/devices/system/cpu/cpuX/topology/thread_siblings: internel kernel map of cpuX's hardware threads within the same core as cpuX -4) /sys/devices/system/cpu/cpuX/topology/core_siblings: +5) /sys/devices/system/cpu/cpuX/topology/core_siblings: internal kernel map of cpuX's hardware threads within the same physical_package_id. +6) /sys/devices/system/cpu/cpuX/topology/book_siblings: + + internal kernel map of cpuX's hardware threads within the same + book_id. + To implement it in an architecture-neutral way, a new source file, -drivers/base/topology.c, is to export the 4 attributes. +drivers/base/topology.c, is to export the 4 or 6 attributes. The two book +related sysfs files will only be created if CONFIG_SCHED_BOOK is selected. For an architecture to support this feature, it must define some of these macros in include/asm-XXX/topology.h: #define topology_physical_package_id(cpu) #define topology_core_id(cpu) +#define topology_book_id(cpu) #define topology_thread_cpumask(cpu) #define topology_core_cpumask(cpu) +#define topology_book_cpumask(cpu) The type of **_id is int. The type of siblings is (const) struct cpumask *. @@ -45,6 +59,9 @@ not defined by include/asm-XXX/topology.h: 3) thread_siblings: just the given CPU 4) core_siblings: just the given CPU +For architectures that don't support books (CONFIG_SCHED_BOOK) there are no +default definitions for topology_book_id() and topology_book_cpumask(). + Additionally, CPU topology information is provided under /sys/devices/system/cpu and includes these files. The internal source for the output is in brackets ("[]"). diff --git a/Documentation/devices.txt b/Documentation/devices.txt index 3cab6b342017..c58abf1ccc71 100644 --- a/Documentation/devices.txt +++ b/Documentation/devices.txt @@ -239,6 +239,7 @@ Your cooperation is appreciated. 0 = /dev/tty Current TTY device 1 = /dev/console System console 2 = /dev/ptmx PTY master multiplex + 3 = /dev/ttyprintk User messages via printk TTY device 64 = /dev/cua0 Callout device for ttyS0 ... 255 = /dev/cua191 Callout device for ttyS191 diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt index 674c5663d346..58ea64a96165 100644 --- a/Documentation/dynamic-debug-howto.txt +++ b/Documentation/dynamic-debug-howto.txt @@ -24,7 +24,7 @@ Dynamic debug has even more useful features: read to display the complete list of known debug statements, to help guide you Controlling dynamic debug Behaviour -=============================== +=================================== The behaviour of pr_debug()/dev_debug()s are controlled via writing to a control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs @@ -212,6 +212,26 @@ Note the regexp ^[-+=][scp]+$ matches a flags specification. Note also that there is no convenient syntax to remove all the flags at once, you need to use "-psc". + +Debug messages during boot process +================================== + +To be able to activate debug messages during the boot process, +even before userspace and debugfs exists, use the boot parameter: +ddebug_query="QUERY" + +QUERY follows the syntax described above, but must not exceed 1023 +characters. The enablement of debug messages is done as an arch_initcall. +Thus you can enable debug messages in all code processed after this +arch_initcall via this boot parameter. +On an x86 system for example ACPI enablement is a subsys_initcall and +ddebug_query="file ec.c +p" +will show early Embedded Controller transactions during ACPI setup if +your machine (typically a laptop) has an Embedded Controller. +PCI (or other devices) initialization also is a hot candidate for using +this boot parameter for debugging purposes. + + Examples ======== diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 842aa9de84a6..5e2bc4ab897a 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -386,34 +386,6 @@ Who: Tejun Heo <tj@kernel.org> ---------------------------- -What: Support for VMware's guest paravirtuliazation technique [VMI] will be - dropped. -When: 2.6.37 or earlier. -Why: With the recent innovations in CPU hardware acceleration technologies - from Intel and AMD, VMware ran a few experiments to compare these - techniques to guest paravirtualization technique on VMware's platform. - These hardware assisted virtualization techniques have outperformed the - performance benefits provided by VMI in most of the workloads. VMware - expects that these hardware features will be ubiquitous in a couple of - years, as a result, VMware has started a phased retirement of this - feature from the hypervisor. We will be removing this feature from the - Kernel too. Right now we are targeting 2.6.37 but can retire earlier if - technical reasons (read opportunity to remove major chunk of pvops) - arise. - - Please note that VMI has always been an optimization and non-VMI kernels - still work fine on VMware's platform. - Latest versions of VMware's product which support VMI are, - Workstation 7.0 and VSphere 4.0 on ESX side, future maintainence - releases for these products will continue supporting VMI. - - For more details about VMI retirement take a look at this, - http://blogs.vmware.com/guestosguide/2009/09/vmi-retirement.html - -Who: Alok N Kataria <akataria@vmware.com> - ----------------------------- - What: Support for lcd_switch and display_get in asus-laptop driver When: March 2010 Why: These two features use non-standard interfaces. There are the diff --git a/Documentation/filesystems/ocfs2.txt b/Documentation/filesystems/ocfs2.txt index 1f7ae144f6d8..5393e6611691 100644 --- a/Documentation/filesystems/ocfs2.txt +++ b/Documentation/filesystems/ocfs2.txt @@ -87,3 +87,10 @@ dir_resv_level= (*) By default, directory reservations will scale with file reservations - users should rarely need to change this value. If allocation reservations are turned off, this option will have no effect. +coherency=full (*) Disallow concurrent O_DIRECT writes, cluster inode + lock will be taken to force other nodes drop cache, + therefore full cluster coherency is guaranteed even + for O_DIRECT writes. +coherency=buffered Allow concurrent O_DIRECT writes without EX lock among + nodes, which gains high performance at risk of getting + stale data on other nodes. diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index a6aca8740883..98223a676940 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1075,6 +1075,7 @@ Table 1-11: Files in /proc/tty drivers list of drivers and their usage ldiscs registered line disciplines driver/serial usage statistic and status of single tty lines + consoles registered system console lines .............................................................................. To see which tty's are currently in use, you can simply look into the file @@ -1093,6 +1094,37 @@ To see which tty's are currently in use, you can simply look into the file /dev/tty /dev/tty 5 0 system:/dev/tty unknown /dev/tty 4 1-63 console +To see which character device lines are currently used for the system console +/dev/console, you may simply look into the file /proc/tty/consoles: + + > cat /proc/tty/consoles + tty0 -WU (ECp) 4:7 + ttyS0 -W- (Ep) 4:64 + +The columns are: + + device name of the device + operations R = can do read operations + W = can do write operations + U = can do unblank + flags E = it is enabled + C = it is prefered console + B = it is primary boot console + p = it is used for printk buffer + b = it is not a TTY but a Braille device + a = it is safe to use when cpu is offline + * = it is standard input of the reading process + major:minor major and minor number of the device separated by a colon + +If the reading process holds /dev/console open at the regular standard input +stream the active device will be marked by an asterisk: + + > cat /proc/tty/consoles < /dev/console + tty0 -WU (ECp*) 4:7 + ttyS0 -W- (Ep) 4:64 + > tty + /dev/pts/3 + 1.8 Miscellaneous kernel statistics in /proc/stat ------------------------------------------------- diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 8dd7248508a9..4cd8b86e00ea 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -43,10 +43,11 @@ parameter is applicable: AVR32 AVR32 architecture is enabled. AX25 Appropriate AX.25 support is enabled. BLACKFIN Blackfin architecture is enabled. - DRM Direct Rendering Management support is enabled. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled EFI EFI Partitioning (GPT) is enabled EIDE EIDE/ATAPI support is enabled. + DRM Direct Rendering Management support is enabled. + DYNAMIC_DEBUG Build in debug messages and enable them at runtime FB The frame buffer device is enabled. GCOV GCOV profiling is enabled. HW Appropriate hardware is enabled. @@ -455,7 +456,7 @@ and is between 256 and 4096 characters. It is defined in the file [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, pxa_timer,timer3,32k_counter,timer0_1 [AVR32] avr32 - [X86-32] pit,hpet,tsc,vmi-timer; + [X86-32] pit,hpet,tsc; scx200_hrt on Geode; cyclone on IBM x440 [MIPS] MIPS [PARISC] cr16 @@ -570,6 +571,10 @@ and is between 256 and 4096 characters. It is defined in the file Format: <port#>,<type> See also Documentation/input/joystick-parport.txt + ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot + time. See Documentation/dynamic-debug-howto.txt for + details. + debug [KNL] Enable kernel debugging (events log level). debug_locks_verbose= @@ -2153,6 +2158,11 @@ and is between 256 and 4096 characters. It is defined in the file Reserves a hole at the top of the kernel virtual address space. + reservelow= [X86] + Format: nn[K] + Set the amount of memory to reserve for BIOS at + the bottom of the address space. + reset_devices [KNL] Force drivers to reset the underlying device during initialization. @@ -2165,6 +2175,11 @@ and is between 256 and 4096 characters. It is defined in the file in <PAGE_SIZE> units (needed only for swap files). See Documentation/power/swsusp-and-swap-files.txt + hibernate= [HIBERNATION] + noresume Don't check if there's a hibernation image + present during boot. + nocompress Don't compress/decompress hibernation images. + retain_initrd [RAM] Keep initrd memory after extraction rhash_entries= [KNL,NET] @@ -2360,6 +2375,15 @@ and is between 256 and 4096 characters. It is defined in the file switches= [HW,M68k] + sysfs.deprecated=0|1 [KNL] + Enable/disable old style sysfs layout for old udev + on older distributions. When this option is enabled + very new udev will not work anymore. When this option + is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) + in older udev will not work anymore. + Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in + the kernel configuration. + sysrq_always_enabled [KNL] Ignore sysrq setting - this boot parameter will @@ -2435,6 +2459,10 @@ and is between 256 and 4096 characters. It is defined in the file disables clocksource verification at runtime. Used to enable high-resolution timer mode on older hardware, and in virtualized environment. + [x86] noirqtime: Do not use TSC to do irq accounting. + Used to run time disable IRQ_TIME_ACCOUNTING on any + platforms where RDTSC is slow and this accounting + can add overhead. turbografx.map[2|3]= [HW,JOY] TurboGraFX parallel port interface diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index 1762b81fcdf2..741fe66d6eca 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -542,9 +542,11 @@ Kprobes does not use mutexes or allocate memory except during registration and unregistration. Probe handlers are run with preemption disabled. Depending on the -architecture, handlers may also run with interrupts disabled. In any -case, your handler should not yield the CPU (e.g., by attempting to -acquire a semaphore). +architecture and optimization state, handlers may also run with +interrupts disabled (e.g., kretprobe handlers and optimized kprobe +handlers run without interrupt disabled on x86/x86-64). In any case, +your handler should not yield the CPU (e.g., by attempting to acquire +a semaphore). Since a return probe is implemented by replacing the return address with the trampoline's address, stack backtraces and calls diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 8a6a8c6d4980..dc73bc54cc4e 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -1640,15 +1640,6 @@ static void blk_request(struct virtqueue *vq) off = out->sector * 512; /* - * The block device implements "barriers", where the Guest indicates - * that it wants all previous writes to occur before this write. We - * don't have a way of asking our kernel to do a barrier, so we just - * synchronize all the data in the file. Pretty poor, no? - */ - if (out->type & VIRTIO_BLK_T_BARRIER) - fdatasync(vblk->fd); - - /* * In general the virtio block driver is allowed to try SCSI commands. * It'd be nice if we supported eject, for example, but we don't. */ @@ -1680,6 +1671,13 @@ static void blk_request(struct virtqueue *vq) /* Die, bad Guest, die. */ errx(1, "Write past end %llu+%u", off, ret); } + + wlen = sizeof(*in); + *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); + } else if (out->type & VIRTIO_BLK_T_FLUSH) { + /* Flush */ + ret = fdatasync(vblk->fd); + verbose("FLUSH fdatasync: %i\n", ret); wlen = sizeof(*in); *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); } else { @@ -1703,15 +1701,6 @@ static void blk_request(struct virtqueue *vq) } } - /* - * OK, so we noted that it was pretty poor to use an fdatasync as a - * barrier. But Christoph Hellwig points out that we need a sync - * *afterwards* as well: "Barriers specify no reordering to the front - * or the back." And Jens Axboe confirmed it, so here we are: - */ - if (out->type & VIRTIO_BLK_T_BARRIER) - fdatasync(vblk->fd); - /* Finished that request. */ add_used(vq, head, wlen); } @@ -1736,8 +1725,8 @@ static void setup_block_file(const char *filename) vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE); vblk->len = lseek64(vblk->fd, 0, SEEK_END); - /* We support barriers. */ - add_feature(dev, VIRTIO_BLK_F_BARRIER); + /* We support FLUSH. */ + add_feature(dev, VIRTIO_BLK_F_FLUSH); /* Tell Guest how many sectors this device has. */ conf.capacity = cpu_to_le64(vblk->len / 512); diff --git a/Documentation/pcmcia/driver-changes.txt b/Documentation/pcmcia/driver-changes.txt index 26c0f9c00545..dd04361dd361 100644 --- a/Documentation/pcmcia/driver-changes.txt +++ b/Documentation/pcmcia/driver-changes.txt @@ -1,4 +1,29 @@ This file details changes in 2.6 which affect PCMCIA card driver authors: +* pcmcia_loop_config() and autoconfiguration (as of 2.6.36) + If struct pcmcia_device *p_dev->config_flags is set accordingly, + pcmcia_loop_config() now sets up certain configuration values + automatically, though the driver may still override the settings + in the callback function. The following autoconfiguration options + are provided at the moment: + CONF_AUTO_CHECK_VCC : check for matching Vcc + CONF_AUTO_SET_VPP : set Vpp + CONF_AUTO_AUDIO : auto-enable audio line, if required + CONF_AUTO_SET_IO : set ioport resources (->resource[0,1]) + CONF_AUTO_SET_IOMEM : set first iomem resource (->resource[2]) + +* pcmcia_request_configuration -> pcmcia_enable_device (as of 2.6.36) + pcmcia_request_configuration() got renamed to pcmcia_enable_device(), + as it mirrors pcmcia_disable_device(). Configuration settings are now + stored in struct pcmcia_device, e.g. in the fields config_flags, + config_index, config_base, vpp. + +* pcmcia_request_window changes (as of 2.6.36) + Instead of win_req_t, drivers are now requested to fill out + struct pcmcia_device *p_dev->resource[2,3,4,5] for up to four ioport + ranges. After a call to pcmcia_request_window(), the regions found there + are reserved and may be used immediately -- until pcmcia_release_window() + is called. + * pcmcia_request_io changes (as of 2.6.36) Instead of io_req_t, drivers are now requested to fill out struct pcmcia_device *p_dev->resource[0,1] for up to two ioport diff --git a/Documentation/power/00-INDEX b/Documentation/power/00-INDEX index fb742c213c9e..45e9d4a91284 100644 --- a/Documentation/power/00-INDEX +++ b/Documentation/power/00-INDEX @@ -14,6 +14,8 @@ interface.txt - Power management user interface in /sys/power notifiers.txt - Registering suspend notifiers in device drivers +opp.txt + - Operating Performance Point library pci.txt - How the PCI Subsystem Does Power Management pm_qos_interface.txt diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt index e67211fe0ee2..c537834af005 100644 --- a/Documentation/power/interface.txt +++ b/Documentation/power/interface.txt @@ -57,7 +57,7 @@ smallest image possible. In particular, if "0" is written to this file, the suspend image will be as small as possible. Reading from this file will display the current image size limit, which -is set to 500 MB by default. +is set to 2/5 of available RAM by default. /sys/power/pm_trace controls the code which saves the last PM event point in the RTC across reboots, so that you can debug a machine that just hangs diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt new file mode 100644 index 000000000000..44d87ad3cea9 --- /dev/null +++ b/Documentation/power/opp.txt @@ -0,0 +1,375 @@ +*=============* +* OPP Library * +*=============* + +(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated + +Contents +-------- +1. Introduction +2. Initial OPP List Registration +3. OPP Search Functions +4. OPP Availability Control Functions +5. OPP Data Retrieval Functions +6. Cpufreq Table Generation +7. Data Structures + +1. Introduction +=============== +Complex SoCs of today consists of a multiple sub-modules working in conjunction. +In an operational system executing varied use cases, not all modules in the SoC +need to function at their highest performing frequency all the time. To +facilitate this, sub-modules in a SoC are grouped into domains, allowing some +domains to run at lower voltage and frequency while other domains are loaded +more. The set of discrete tuples consisting of frequency and voltage pairs that +the device will support per domain are called Operating Performance Points or +OPPs. + +OPP library provides a set of helper functions to organize and query the OPP +information. The library is located in drivers/base/power/opp.c and the header +is located in include/linux/opp.h. OPP library can be enabled by enabling +CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on +CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to +optionally boot at a certain OPP without needing cpufreq. + +Typical usage of the OPP library is as follows: +(users) -> registers a set of default OPPs -> (library) +SoC framework -> modifies on required cases certain OPPs -> OPP layer + -> queries to search/retrieve information -> + +OPP layer expects each domain to be represented by a unique device pointer. SoC +framework registers a set of initial OPPs per device with the OPP layer. This +list is expected to be an optimally small number typically around 5 per device. +This initial list contains a set of OPPs that the framework expects to be safely +enabled by default in the system. + +Note on OPP Availability: +------------------------ +As the system proceeds to operate, SoC framework may choose to make certain +OPPs available or not available on each device based on various external +factors. Example usage: Thermal management or other exceptional situations where +SoC framework might choose to disable a higher frequency OPP to safely continue +operations until that OPP could be re-enabled if possible. + +OPP library facilitates this concept in it's implementation. The following +operational functions operate only on available opps: +opp_find_freq_{ceil, floor}, opp_get_voltage, opp_get_freq, opp_get_opp_count +and opp_init_cpufreq_table + +opp_find_freq_exact is meant to be used to find the opp pointer which can then +be used for opp_enable/disable functions to make an opp available as required. + +WARNING: Users of OPP library should refresh their availability count using +get_opp_count if opp_enable/disable functions are invoked for a device, the +exact mechanism to trigger these or the notification mechanism to other +dependent subsystems such as cpufreq are left to the discretion of the SoC +specific framework which uses the OPP library. Similar care needs to be taken +care to refresh the cpufreq table in cases of these operations. + +WARNING on OPP List locking mechanism: +------------------------------------------------- +OPP library uses RCU for exclusivity. RCU allows the query functions to operate +in multiple contexts and this synchronization mechanism is optimal for a read +intensive operations on data structure as the OPP library caters to. + +To ensure that the data retrieved are sane, the users such as SoC framework +should ensure that the section of code operating on OPP queries are locked +using RCU read locks. The opp_find_freq_{exact,ceil,floor}, +opp_get_{voltage, freq, opp_count} fall into this category. + +opp_{add,enable,disable} are updaters which use mutex and implement it's own +RCU locking mechanisms. opp_init_cpufreq_table acts as an updater and uses +mutex to implment RCU updater strategy. These functions should *NOT* be called +under RCU locks and other contexts that prevent blocking functions in RCU or +mutex operations from working. + +2. Initial OPP List Registration +================================ +The SoC implementation calls opp_add function iteratively to add OPPs per +device. It is expected that the SoC framework will register the OPP entries +optimally- typical numbers range to be less than 5. The list generated by +registering the OPPs is maintained by OPP library throughout the device +operation. The SoC framework can subsequently control the availability of the +OPPs dynamically using the opp_enable / disable functions. + +opp_add - Add a new OPP for a specific domain represented by the device pointer. + The OPP is defined using the frequency and voltage. Once added, the OPP + is assumed to be available and control of it's availability can be done + with the opp_enable/disable functions. OPP library internally stores + and manages this information in the opp struct. This function may be + used by SoC framework to define a optimal list as per the demands of + SoC usage environment. + + WARNING: Do not use this function in interrupt context. + + Example: + soc_pm_init() + { + /* Do things */ + r = opp_add(mpu_dev, 1000000, 900000); + if (!r) { + pr_err("%s: unable to register mpu opp(%d)\n", r); + goto no_cpufreq; + } + /* Do cpufreq things */ + no_cpufreq: + /* Do remaining things */ + } + +3. OPP Search Functions +======================= +High level framework such as cpufreq operates on frequencies. To map the +frequency back to the corresponding OPP, OPP library provides handy functions +to search the OPP list that OPP library internally manages. These search +functions return the matching pointer representing the opp if a match is +found, else returns error. These errors are expected to be handled by standard +error checks such as IS_ERR() and appropriate actions taken by the caller. + +opp_find_freq_exact - Search for an OPP based on an *exact* frequency and + availability. This function is especially useful to enable an OPP which + is not available by default. + Example: In a case when SoC framework detects a situation where a + higher frequency could be made available, it can use this function to + find the OPP prior to call the opp_enable to actually make it available. + rcu_read_lock(); + opp = opp_find_freq_exact(dev, 1000000000, false); + rcu_read_unlock(); + /* dont operate on the pointer.. just do a sanity check.. */ + if (IS_ERR(opp)) { + pr_err("frequency not disabled!\n"); + /* trigger appropriate actions.. */ + } else { + opp_enable(dev,1000000000); + } + + NOTE: This is the only search function that operates on OPPs which are + not available. + +opp_find_freq_floor - Search for an available OPP which is *at most* the + provided frequency. This function is useful while searching for a lesser + match OR operating on OPP information in the order of decreasing + frequency. + Example: To find the highest opp for a device: + freq = ULONG_MAX; + rcu_read_lock(); + opp_find_freq_floor(dev, &freq); + rcu_read_unlock(); + +opp_find_freq_ceil - Search for an available OPP which is *at least* the + provided frequency. This function is useful while searching for a + higher match OR operating on OPP information in the order of increasing + frequency. + Example 1: To find the lowest opp for a device: + freq = 0; + rcu_read_lock(); + opp_find_freq_ceil(dev, &freq); + rcu_read_unlock(); + Example 2: A simplified implementation of a SoC cpufreq_driver->target: + soc_cpufreq_target(..) + { + /* Do stuff like policy checks etc. */ + /* Find the best frequency match for the req */ + rcu_read_lock(); + opp = opp_find_freq_ceil(dev, &freq); + rcu_read_unlock(); + if (!IS_ERR(opp)) + soc_switch_to_freq_voltage(freq); + else + /* do something when we cant satisfy the req */ + /* do other stuff */ + } + +4. OPP Availability Control Functions +===================================== +A default OPP list registered with the OPP library may not cater to all possible +situation. The OPP library provides a set of functions to modify the +availability of a OPP within the OPP list. This allows SoC frameworks to have +fine grained dynamic control of which sets of OPPs are operationally available. +These functions are intended to *temporarily* remove an OPP in conditions such +as thermal considerations (e.g. don't use OPPx until the temperature drops). + +WARNING: Do not use these functions in interrupt context. + +opp_enable - Make a OPP available for operation. + Example: Lets say that 1GHz OPP is to be made available only if the + SoC temperature is lower than a certain threshold. The SoC framework + implementation might choose to do something as follows: + if (cur_temp < temp_low_thresh) { + /* Enable 1GHz if it was disabled */ + rcu_read_lock(); + opp = opp_find_freq_exact(dev, 1000000000, false); + rcu_read_unlock(); + /* just error check */ + if (!IS_ERR(opp)) + ret = opp_enable(dev, 1000000000); + else + goto try_something_else; + } + +opp_disable - Make an OPP to be not available for operation + Example: Lets say that 1GHz OPP is to be disabled if the temperature + exceeds a threshold value. The SoC framework implementation might + choose to do something as follows: + if (cur_temp > temp_high_thresh) { + /* Disable 1GHz if it was enabled */ + rcu_read_lock(); + opp = opp_find_freq_exact(dev, 1000000000, true); + rcu_read_unlock(); + /* just error check */ + if (!IS_ERR(opp)) + ret = opp_disable(dev, 1000000000); + else + goto try_something_else; + } + +5. OPP Data Retrieval Functions +=============================== +Since OPP library abstracts away the OPP information, a set of functions to pull +information from the OPP structure is necessary. Once an OPP pointer is +retrieved using the search functions, the following functions can be used by SoC +framework to retrieve the information represented inside the OPP layer. + +opp_get_voltage - Retrieve the voltage represented by the opp pointer. + Example: At a cpufreq transition to a different frequency, SoC + framework requires to set the voltage represented by the OPP using + the regulator framework to the Power Management chip providing the + voltage. + soc_switch_to_freq_voltage(freq) + { + /* do things */ + rcu_read_lock(); + opp = opp_find_freq_ceil(dev, &freq); + v = opp_get_voltage(opp); + rcu_read_unlock(); + if (v) + regulator_set_voltage(.., v); + /* do other things */ + } + +opp_get_freq - Retrieve the freq represented by the opp pointer. + Example: Lets say the SoC framework uses a couple of helper functions + we could pass opp pointers instead of doing additional parameters to + handle quiet a bit of data parameters. + soc_cpufreq_target(..) + { + /* do things.. */ + max_freq = ULONG_MAX; + rcu_read_lock(); + max_opp = opp_find_freq_floor(dev,&max_freq); + requested_opp = opp_find_freq_ceil(dev,&freq); + if (!IS_ERR(max_opp) && !IS_ERR(requested_opp)) + r = soc_test_validity(max_opp, requested_opp); + rcu_read_unlock(); + /* do other things */ + } + soc_test_validity(..) + { + if(opp_get_voltage(max_opp) < opp_get_voltage(requested_opp)) + return -EINVAL; + if(opp_get_freq(max_opp) < opp_get_freq(requested_opp)) + return -EINVAL; + /* do things.. */ + } + +opp_get_opp_count - Retrieve the number of available opps for a device + Example: Lets say a co-processor in the SoC needs to know the available + frequencies in a table, the main processor can notify as following: + soc_notify_coproc_available_frequencies() + { + /* Do things */ + rcu_read_lock(); + num_available = opp_get_opp_count(dev); + speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL); + /* populate the table in increasing order */ + freq = 0; + while (!IS_ERR(opp = opp_find_freq_ceil(dev, &freq))) { + speeds[i] = freq; + freq++; + i++; + } + rcu_read_unlock(); + + soc_notify_coproc(AVAILABLE_FREQs, speeds, num_available); + /* Do other things */ + } + +6. Cpufreq Table Generation +=========================== +opp_init_cpufreq_table - cpufreq framework typically is initialized with + cpufreq_frequency_table_cpuinfo which is provided with the list of + frequencies that are available for operation. This function provides + a ready to use conversion routine to translate the OPP layer's internal + information about the available frequencies into a format readily + providable to cpufreq. + + WARNING: Do not use this function in interrupt context. + + Example: + soc_pm_init() + { + /* Do things */ + r = opp_init_cpufreq_table(dev, &freq_table); + if (!r) + cpufreq_frequency_table_cpuinfo(policy, freq_table); + /* Do other things */ + } + + NOTE: This function is available only if CONFIG_CPU_FREQ is enabled in + addition to CONFIG_PM as power management feature is required to + dynamically scale voltage and frequency in a system. + +7. Data Structures +================== +Typically an SoC contains multiple voltage domains which are variable. Each +domain is represented by a device pointer. The relationship to OPP can be +represented as follows: +SoC + |- device 1 + | |- opp 1 (availability, freq, voltage) + | |- opp 2 .. + ... ... + | `- opp n .. + |- device 2 + ... + `- device m + +OPP library maintains a internal list that the SoC framework populates and +accessed by various functions as described above. However, the structures +representing the actual OPPs and domains are internal to the OPP library itself +to allow for suitable abstraction reusable across systems. + +struct opp - The internal data structure of OPP library which is used to + represent an OPP. In addition to the freq, voltage, availability + information, it also contains internal book keeping information required + for the OPP library to operate on. Pointer to this structure is + provided back to the users such as SoC framework to be used as a + identifier for OPP in the interactions with OPP layer. + + WARNING: The struct opp pointer should not be parsed or modified by the + users. The defaults of for an instance is populated by opp_add, but the + availability of the OPP can be modified by opp_enable/disable functions. + +struct device - This is used to identify a domain to the OPP layer. The + nature of the device and it's implementation is left to the user of + OPP library such as the SoC framework. + +Overall, in a simplistic view, the data structure operations is represented as +following: + +Initialization / modification: + +-----+ /- opp_enable +opp_add --> | opp | <------- + | +-----+ \- opp_disable + \-------> domain_info(device) + +Search functions: + /-- opp_find_freq_ceil ---\ +-----+ +domain_info<---- opp_find_freq_exact -----> | opp | + \-- opp_find_freq_floor ---/ +-----+ + +Retrieval functions: ++-----+ /- opp_get_voltage +| opp | <--- ++-----+ \- opp_get_freq + +domain_info <- opp_get_opp_count diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 55b859b3bc72..489e9bacd165 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -1,6 +1,7 @@ Run-time Power Management Framework for I/O Devices (C) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc. +(C) 2010 Alan Stern <stern@rowland.harvard.edu> 1. Introduction @@ -157,7 +158,8 @@ rules: to execute it, the other callbacks will not be executed for the same device. * A request to execute ->runtime_resume() will cancel any pending or - scheduled requests to execute the other callbacks for the same device. + scheduled requests to execute the other callbacks for the same device, + except for scheduled autosuspends. 3. Run-time PM Device Fields @@ -165,7 +167,7 @@ The following device run-time PM fields are present in 'struct dev_pm_info', as defined in include/linux/pm.h: struct timer_list suspend_timer; - - timer used for scheduling (delayed) suspend request + - timer used for scheduling (delayed) suspend and autosuspend requests unsigned long timer_expires; - timer expiration time, in jiffies (if this is different from zero, the @@ -230,6 +232,28 @@ defined in include/linux/pm.h: interface; it may only be modified with the help of the pm_runtime_allow() and pm_runtime_forbid() helper functions + unsigned int no_callbacks; + - indicates that the device does not use the run-time PM callbacks (see + Section 8); it may be modified only by the pm_runtime_no_callbacks() + helper function + + unsigned int use_autosuspend; + - indicates that the device's driver supports delayed autosuspend (see + Section 9); it may be modified only by the + pm_runtime{_dont}_use_autosuspend() helper functions + + unsigned int timer_autosuspends; + - indicates that the PM core should attempt to carry out an autosuspend + when the timer expires rather than a normal suspend + + int autosuspend_delay; + - the delay time (in milliseconds) to be used for autosuspend + + unsigned long last_busy; + - the time (in jiffies) when the pm_runtime_mark_last_busy() helper + function was last called for this device; used in calculating inactivity + periods for autosuspend + All of the above fields are members of the 'power' member of 'struct device'. 4. Run-time PM Device Helper Functions @@ -255,6 +279,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt to suspend the device again in future + int pm_runtime_autosuspend(struct device *dev); + - same as pm_runtime_suspend() except that the autosuspend delay is taken + into account; if pm_runtime_autosuspend_expiration() says the delay has + not yet expired then an autosuspend is scheduled for the appropriate time + and 0 is returned + int pm_runtime_resume(struct device *dev); - execute the subsystem-level resume callback for the device; returns 0 on success, 1 if the device's run-time PM status was already 'active' or @@ -267,6 +297,11 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: device (the request is represented by a work item in pm_wq); returns 0 on success or error code if the request has not been queued up + int pm_request_autosuspend(struct device *dev); + - schedule the execution of the subsystem-level suspend callback for the + device when the autosuspend delay has expired; if the delay has already + expired then the work item is queued up immediately + int pm_schedule_suspend(struct device *dev, unsigned int delay); - schedule the execution of the subsystem-level suspend callback for the device in future, where 'delay' is the time to wait before queuing up a @@ -298,12 +333,20 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: - decrement the device's usage counter int pm_runtime_put(struct device *dev); - - decrement the device's usage counter, run pm_request_idle(dev) and return - its result + - decrement the device's usage counter; if the result is 0 then run + pm_request_idle(dev) and return its result + + int pm_runtime_put_autosuspend(struct device *dev); + - decrement the device's usage counter; if the result is 0 then run + pm_request_autosuspend(dev) and return its result int pm_runtime_put_sync(struct device *dev); - - decrement the device's usage counter, run pm_runtime_idle(dev) and return - its result + - decrement the device's usage counter; if the result is 0 then run + pm_runtime_idle(dev) and return its result + + int pm_runtime_put_sync_autosuspend(struct device *dev); + - decrement the device's usage counter; if the result is 0 then run + pm_runtime_autosuspend(dev) and return its result void pm_runtime_enable(struct device *dev); - enable the run-time PM helper functions to run the device bus type's @@ -349,19 +392,51 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: counter (used by the /sys/devices/.../power/control interface to effectively prevent the device from being power managed at run time) + void pm_runtime_no_callbacks(struct device *dev); + - set the power.no_callbacks flag for the device and remove the run-time + PM attributes from /sys/devices/.../power (or prevent them from being + added when the device is registered) + + void pm_runtime_mark_last_busy(struct device *dev); + - set the power.last_busy field to the current time + + void pm_runtime_use_autosuspend(struct device *dev); + - set the power.use_autosuspend flag, enabling autosuspend delays + + void pm_runtime_dont_use_autosuspend(struct device *dev); + - clear the power.use_autosuspend flag, disabling autosuspend delays + + void pm_runtime_set_autosuspend_delay(struct device *dev, int delay); + - set the power.autosuspend_delay value to 'delay' (expressed in + milliseconds); if 'delay' is negative then run-time suspends are + prevented + + unsigned long pm_runtime_autosuspend_expiration(struct device *dev); + - calculate the time when the current autosuspend delay period will expire, + based on power.last_busy and power.autosuspend_delay; if the delay time + is 1000 ms or larger then the expiration time is rounded up to the + nearest second; returns 0 if the delay period has already expired or + power.use_autosuspend isn't set, otherwise returns the expiration time + in jiffies + It is safe to execute the following helper functions from interrupt context: pm_request_idle() +pm_request_autosuspend() pm_schedule_suspend() pm_request_resume() pm_runtime_get_noresume() pm_runtime_get() pm_runtime_put_noidle() pm_runtime_put() +pm_runtime_put_autosuspend() +pm_runtime_enable() pm_suspend_ignore_children() pm_runtime_set_active() pm_runtime_set_suspended() -pm_runtime_enable() +pm_runtime_suspended() +pm_runtime_mark_last_busy() +pm_runtime_autosuspend_expiration() 5. Run-time PM Initialization, Device Probing and Removal @@ -524,3 +599,141 @@ poweroff and run-time suspend callback, and similarly for system resume, thaw, restore, and run-time resume, can achieve this with the help of the UNIVERSAL_DEV_PM_OPS macro defined in include/linux/pm.h (possibly setting its last argument to NULL). + +8. "No-Callback" Devices + +Some "devices" are only logical sub-devices of their parent and cannot be +power-managed on their own. (The prototype example is a USB interface. Entire +USB devices can go into low-power mode or send wake-up requests, but neither is +possible for individual interfaces.) The drivers for these devices have no +need of run-time PM callbacks; if the callbacks did exist, ->runtime_suspend() +and ->runtime_resume() would always return 0 without doing anything else and +->runtime_idle() would always call pm_runtime_suspend(). + +Subsystems can tell the PM core about these devices by calling +pm_runtime_no_callbacks(). This should be done after the device structure is +initialized and before it is registered (although after device registration is +also okay). The routine will set the device's power.no_callbacks flag and +prevent the non-debugging run-time PM sysfs attributes from being created. + +When power.no_callbacks is set, the PM core will not invoke the +->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks. +Instead it will assume that suspends and resumes always succeed and that idle +devices should be suspended. + +As a consequence, the PM core will never directly inform the device's subsystem +or driver about run-time power changes. Instead, the driver for the device's +parent must take responsibility for telling the device's driver when the +parent's power state changes. + +9. Autosuspend, or automatically-delayed suspends + +Changing a device's power state isn't free; it requires both time and energy. +A device should be put in a low-power state only when there's some reason to +think it will remain in that state for a substantial time. A common heuristic +says that a device which hasn't been used for a while is liable to remain +unused; following this advice, drivers should not allow devices to be suspended +at run-time until they have been inactive for some minimum period. Even when +the heuristic ends up being non-optimal, it will still prevent devices from +"bouncing" too rapidly between low-power and full-power states. + +The term "autosuspend" is an historical remnant. It doesn't mean that the +device is automatically suspended (the subsystem or driver still has to call +the appropriate PM routines); rather it means that run-time suspends will +automatically be delayed until the desired period of inactivity has elapsed. + +Inactivity is determined based on the power.last_busy field. Drivers should +call pm_runtime_mark_last_busy() to update this field after carrying out I/O, +typically just before calling pm_runtime_put_autosuspend(). The desired length +of the inactivity period is a matter of policy. Subsystems can set this length +initially by calling pm_runtime_set_autosuspend_delay(), but after device +registration the length should be controlled by user space, using the +/sys/devices/.../power/autosuspend_delay_ms attribute. + +In order to use autosuspend, subsystems or drivers must call +pm_runtime_use_autosuspend() (preferably before registering the device), and +thereafter they should use the various *_autosuspend() helper functions instead +of the non-autosuspend counterparts: + + Instead of: pm_runtime_suspend use: pm_runtime_autosuspend; + Instead of: pm_schedule_suspend use: pm_request_autosuspend; + Instead of: pm_runtime_put use: pm_runtime_put_autosuspend; + Instead of: pm_runtime_put_sync use: pm_runtime_put_sync_autosuspend. + +Drivers may also continue to use the non-autosuspend helper functions; they +will behave normally, not taking the autosuspend delay into account. +Similarly, if the power.use_autosuspend field isn't set then the autosuspend +helper functions will behave just like the non-autosuspend counterparts. + +The implementation is well suited for asynchronous use in interrupt contexts. +However such use inevitably involves races, because the PM core can't +synchronize ->runtime_suspend() callbacks with the arrival of I/O requests. +This synchronization must be handled by the driver, using its private lock. +Here is a schematic pseudo-code example: + + foo_read_or_write(struct foo_priv *foo, void *data) + { + lock(&foo->private_lock); + add_request_to_io_queue(foo, data); + if (foo->num_pending_requests++ == 0) + pm_runtime_get(&foo->dev); + if (!foo->is_suspended) + foo_process_next_request(foo); + unlock(&foo->private_lock); + } + + foo_io_completion(struct foo_priv *foo, void *req) + { + lock(&foo->private_lock); + if (--foo->num_pending_requests == 0) { + pm_runtime_mark_last_busy(&foo->dev); + pm_runtime_put_autosuspend(&foo->dev); + } else { + foo_process_next_request(foo); + } + unlock(&foo->private_lock); + /* Send req result back to the user ... */ + } + + int foo_runtime_suspend(struct device *dev) + { + struct foo_priv foo = container_of(dev, ...); + int ret = 0; + + lock(&foo->private_lock); + if (foo->num_pending_requests > 0) { + ret = -EBUSY; + } else { + /* ... suspend the device ... */ + foo->is_suspended = 1; + } + unlock(&foo->private_lock); + return ret; + } + + int foo_runtime_resume(struct device *dev) + { + struct foo_priv foo = container_of(dev, ...); + + lock(&foo->private_lock); + /* ... resume the device ... */ + foo->is_suspended = 0; + pm_runtime_mark_last_busy(&foo->dev); + if (foo->num_pending_requests > 0) + foo_process_requests(foo); + unlock(&foo->private_lock); + return 0; + } + +The important point is that after foo_io_completion() asks for an autosuspend, +the foo_runtime_suspend() callback may race with foo_read_or_write(). +Therefore foo_runtime_suspend() has to check whether there are any pending I/O +requests (while holding the private lock) before allowing the suspend to +proceed. + +In addition, the power.autosuspend_delay field can be changed by user space at +any time. If a driver cares about this, it can call +pm_runtime_autosuspend_expiration() from within the ->runtime_suspend() +callback while holding its private lock. If the function returns a nonzero +value then the delay has not yet expired and the callback should return +-EAGAIN. diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt index 514b94fc931e..1bdfa0443773 100644 --- a/Documentation/power/s2ram.txt +++ b/Documentation/power/s2ram.txt @@ -49,6 +49,13 @@ machine that doesn't boot) is: device (lspci and /sys/devices/pci* is your friend), and see if you can fix it, disable it, or trace into its resume function. + If no device matches the hash (or any matches appear to be false positives), + the culprit may be a device from a loadable kernel module that is not loaded + until after the hash is checked. You can check the hash against the current + devices again after more modules are loaded using sysfs: + + cat /sys/power/pm_trace_dev_match + For example, the above happens to be the VGA device on my EVO, which I used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out that "radeonfb" simply cannot resume that device - it tries to set the diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt index 9d60ab717a7b..ea718891a665 100644 --- a/Documentation/power/swsusp.txt +++ b/Documentation/power/swsusp.txt @@ -66,7 +66,8 @@ swsusp saves the state of the machine into active swaps and then reboots or powerdowns. You must explicitly specify the swap partition to resume from with ``resume='' kernel option. If signature is found it loads and restores saved state. If the option ``noresume'' is specified as a boot parameter, it skips -the resuming. +the resuming. If the option ``hibernate=nocompress'' is specified as a boot +parameter, it saves hibernation image without compression. In the meantime while the system is suspended you should not add/remove any of the hardware, write to the filesystems, etc. diff --git a/Documentation/powerpc/dts-bindings/fsl/spi.txt b/Documentation/powerpc/dts-bindings/fsl/spi.txt index 80510c018eea..777abd7399d5 100644 --- a/Documentation/powerpc/dts-bindings/fsl/spi.txt +++ b/Documentation/powerpc/dts-bindings/fsl/spi.txt @@ -1,7 +1,9 @@ * SPI (Serial Peripheral Interface) Required properties: -- cell-index : SPI controller index. +- cell-index : QE SPI subblock index. + 0: QE subblock SPI1 + 1: QE subblock SPI2 - compatible : should be "fsl,spi". - mode : the SPI operation mode, it can be "cpu" or "cpu-qe". - reg : Offset and length of the register set for the device @@ -29,3 +31,23 @@ Example: gpios = <&gpio 18 1 // device reg=<0> &gpio 19 1>; // device reg=<1> }; + + +* eSPI (Enhanced Serial Peripheral Interface) + +Required properties: +- compatible : should be "fsl,mpc8536-espi". +- reg : Offset and length of the register set for the device. +- interrupts : should contain eSPI interrupt, the device has one interrupt. +- fsl,espi-num-chipselects : the number of the chipselect signals. + +Example: + spi@110000 { + #address-cells = <1>; + #size-cells = <0>; + compatible = "fsl,mpc8536-espi"; + reg = <0x110000 0x1000>; + interrupts = <53 0x2>; + interrupt-parent = <&mpic>; + fsl,espi-num-chipselects = <4>; + }; diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt index 40752602c050..691ca292c24d 100644 --- a/Documentation/scsi/st.txt +++ b/Documentation/scsi/st.txt @@ -2,7 +2,7 @@ This file contains brief information about the SCSI tape driver. The driver is currently maintained by Kai Mäkisara (email Kai.Makisara@kolumbus.fi) -Last modified: Sun Feb 24 21:59:07 2008 by kai.makisara +Last modified: Sun Aug 29 18:25:47 2010 by kai.makisara BASICS @@ -85,6 +85,17 @@ writing and the last operation has been a write. Two filemarks can be optionally written. In both cases end of data is signified by returning zero bytes for two consecutive reads. +Writing filemarks without the immediate bit set in the SCSI command block acts +as a synchronization point, i.e., all remaining data form the drive buffers is +written to tape before the command returns. This makes sure that write errors +are caught at that point, but this takes time. In some applications, several +consecutive files must be written fast. The MTWEOFI operation can be used to +write the filemarks without flushing the drive buffer. Writing filemark at +close() is always flushing the drive buffers. However, if the previous +operation is MTWEOFI, close() does not write a filemark. This can be used if +the program wants to close/open the tape device between files and wants to +skip waiting. + If rewind, offline, bsf, or seek is done and previous tape operation was write, a filemark is written before moving tape. @@ -301,6 +312,8 @@ MTBSR Space backward over count records. MTFSS Space forward over count setmarks. MTBSS Space backward over count setmarks. MTWEOF Write count filemarks. +MTWEOFI Write count filemarks with immediate bit set (i.e., does not + wait until data is on tape) MTWSM Write count setmarks. MTREW Rewind tape. MTOFFL Set device off line (often rewind plus eject). diff --git a/Documentation/workqueue.txt b/Documentation/workqueue.txt index e4498a2872c3..996a27d9b8db 100644 --- a/Documentation/workqueue.txt +++ b/Documentation/workqueue.txt @@ -196,11 +196,11 @@ resources, scheduled and executed. suspend operations. Work items on the wq are drained and no new work item starts execution until thawed. - WQ_RESCUER + WQ_MEM_RECLAIM All wq which might be used in the memory reclaim paths _MUST_ - have this flag set. This reserves one worker exclusively for - the execution of this wq under memory pressure. + have this flag set. The wq is guaranteed to have at least one + execution context regardless of memory pressure. WQ_HIGHPRI @@ -356,11 +356,11 @@ If q1 has WQ_CPU_INTENSIVE set, 6. Guidelines -* Do not forget to use WQ_RESCUER if a wq may process work items which - are used during memory reclaim. Each wq with WQ_RESCUER set has one - rescuer thread reserved for it. If there is dependency among - multiple work items used during memory reclaim, they should be - queued to separate wq each with WQ_RESCUER. +* Do not forget to use WQ_MEM_RECLAIM if a wq may process work items + which are used during memory reclaim. Each wq with WQ_MEM_RECLAIM + set has an execution context reserved for it. If there is + dependency among multiple work items used during memory reclaim, + they should be queued to separate wq each with WQ_MEM_RECLAIM. * Unless strict ordering is required, there is no need to use ST wq. @@ -368,12 +368,13 @@ If q1 has WQ_CPU_INTENSIVE set, recommended. In most use cases, concurrency level usually stays well under the default limit. -* A wq serves as a domain for forward progress guarantee (WQ_RESCUER), - flush and work item attributes. Work items which are not involved - in memory reclaim and don't need to be flushed as a part of a group - of work items, and don't require any special attribute, can use one - of the system wq. There is no difference in execution - characteristics between using a dedicated wq and a system wq. +* A wq serves as a domain for forward progress guarantee + (WQ_MEM_RECLAIM, flush and work item attributes. Work items which + are not involved in memory reclaim and don't need to be flushed as a + part of a group of work items, and don't require any special + attribute, can use one of the system wq. There is no difference in + execution characteristics between using a dedicated wq and a system + wq. * Unless work items are expected to consume a huge amount of CPU cycles, using a bound wq is usually beneficial due to the increased diff --git a/Documentation/x86/x86_64/kernel-stacks b/Documentation/x86/x86_64/kernel-stacks index 5ad65d51fb95..a01eec5d1d0b 100644 --- a/Documentation/x86/x86_64/kernel-stacks +++ b/Documentation/x86/x86_64/kernel-stacks @@ -18,9 +18,9 @@ specialized stacks contain no useful data. The main CPU stacks are: Used for external hardware interrupts. If this is the first external hardware interrupt (i.e. not a nested hardware interrupt) then the kernel switches from the current task to the interrupt stack. Like - the split thread and interrupt stacks on i386 (with CONFIG_4KSTACKS), - this gives more room for kernel interrupt processing without having - to increase the size of every per thread stack. + the split thread and interrupt stacks on i386, this gives more room + for kernel interrupt processing without having to increase the size + of every per thread stack. The interrupt stack is also used when processing a softirq. |