linux-toradex.git/kernel/time/clocksource.c, branch v2.6.33.1

clocksource: Prevent potential kgdb dead lock

2010-01-26T13:53:16+00:00

commit 0f8e8ef7 (clocksource: Simplify clocksource watchdog resume
logic) introduced a potential kgdb dead lock. When the kernel is
stopped by kgdb inside code which holds watchdog_lock then kgdb dead
locks in clocksource_resume_watchdog().

clocksource_resume_watchdog() is called from kbdg via
clocksource_touch_watchdog() to avoid that the clock source watchdog
marks TSC unstable after the kernel has been stopped.

Solve this by replacing spin_lock with a spin_trylock and just return
in case the lock is held. Not resetting the watchdog might result in
TSC becoming marked unstable, but that's an acceptable penalty for
using kgdb.

The timekeeping is anyway easily screwed up by kgdb when the system
uses either jiffies or a clock source which wraps in short intervals
(e.g. pm_timer wraps about every 4.6s), so we really do not have to
worry about that occasional TSC marked unstable side effect.

The second caller of clocksource_resume_watchdog() is
clocksource_resume(). The trylock is safe here as well because the
system is UP at this point, interrupts are disabled and nothing else
can hold watchdog_lock().

Reported-by: Jason Wessel 
LKML-Reference: <1264480000-6997-4-git-send-email-jason.wessel@windriver.com>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: Martin Schwidefsky 
Cc: John Stultz 
Cc: Andrew Morton 
Signed-off-by: Thomas Gleixner

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

2009-12-10T03:43:33+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (42 commits)
  tree-wide: fix misspelling of "definition" in comments
  reiserfs: fix misspelling of "journaled"
  doc: Fix a typo in slub.txt.
  inotify: remove superfluous return code check
  hdlc: spelling fix in find_pvc() comment
  doc: fix regulator docs cut-and-pasteism
  mtd: Fix comment in Kconfig
  doc: Fix IRQ chip docs
  tree-wide: fix assorted typos all over the place
  drivers/ata/libata-sff.c: comment spelling fixes
  fix typos/grammos in Documentation/edac.txt
  sysctl: add missing comments
  fs/debugfs/inode.c: fix comment typos
  sgivwfb: Make use of ARRAY_SIZE.
  sky2: fix sky2_link_down copy/paste comment error
  tree-wide: fix typos "couter" -> "counter"
  tree-wide: fix typos "offest" -> "offset"
  fix kerneldoc for set_irq_msi()
  spidev: fix double "of of" in comment
  comment typo fix: sybsystem -> subsystem
  ...

Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2009-12-09T03:27:08+00:00

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  timers, init: Limit the number of per cpu calibration bootup messages
  posix-cpu-timers: optimize and document timer_create callback
  clockevents: Add missing include to pacify sparse
  x86: vmiclock: Fix printk format
  x86: Fix printk format due to variable type change
  sparc: fix printk for change of variable type
  clocksource/events: Fix fallout of generic code changes
  nohz: Allow 32-bit machines to sleep for more than 2.15 seconds
  nohz: Track last do_timer() cpu
  nohz: Prevent clocksource wrapping during idle
  nohz: Type cast printk argument
  mips: Use generic mult/shift factor calculation for clocks
  clocksource: Provide a generic mult/shift factor calculation
  clockevents: Use u32 for mult and shift factors
  nohz: Introduce arch_needs_cpu
  nohz: Reuse ktime in sub-functions of tick_check_idle.
  time: Remove xtime_cache
  time: Implement logarithmic time accumulation

clocksource/events: Fix fallout of generic code changes

2009-11-13T23:35:52+00:00

powerpc grew a new warning due to the type change of clockevent->mult.

The architectures which use parts of the generic time keeping
infrastructure tripped over my wrong assumption that
clocksource_register is only used when GENERIC_TIME=y.

I should have looked and also I should have known better. These
renitent Gaul villages are racking my nerves. Some serious deprecating
is due.

Signed-off-by: Thomas Gleixner

nohz: Prevent clocksource wrapping during idle

2009-11-13T19:46:24+00:00

The dynamic tick allows the kernel to sleep for periods longer than a
single tick, but it does not limit the sleep time currently. In the
worst case the kernel could sleep longer than the wrap around time of
the time keeping clock source which would result in losing track of
time.

Prevent this by limiting it to the safe maximum sleep time of the
current time keeping clock source. The value is calculated when the
clock source is registered.

[ tglx: simplified the code a bit and massaged the commit msg ]

Signed-off-by: Jon Hunter 
Cc: John Stultz 
LKML-Reference: <1250617512-23567-2-git-send-email-jon-hunter@ti.com>
Signed-off-by: Thomas Gleixner

clocksource: Provide a generic mult/shift factor calculation

2009-11-13T19:46:23+00:00

MIPS has two functions to calculcate the mult/shift factors for clock
sources and clock events at run time. ARM needs such functions as
well.

Implement a function which calculates the mult/shift factors based on
the frequencies to which and from which is converted. The function
also has a parameter to specify the minimum conversion range in
seconds. This range is guaranteed not to produce a 64bit overflow when
a value is multiplied with the calculated mult factor. The larger the
conversion range the less becomes the conversion accuracy.

Provide two inline wrappers which handle clock events and clock
sources. For clock events the "from" frequency is nano seconds per
second which corresponds to 1GHz and "to" is the device frequency. For
clock sources "from" is the device frequency and "to" is nano seconds
per second.

Signed-off-by: Thomas Gleixner 
Tested-by: Mikael Pettersson 
Acked-by: Ralf Baechle 
Acked-by: Linus Walleij 
Cc: John Stultz 
LKML-Reference: <20091111134229.766673305@linutronix.de>

clocksource/timecompare: Fix symbol exports to be GPL'd.

2009-11-12T03:06:30+00:00

Noticed by Thomas GLeixner.

Signed-off-by: David S. Miller

tree-wide: fix typos "selct" + "slect" -> "select"

2009-11-09T08:40:56+00:00

This patch was generated by

	git grep -E -i -l 's(le|el)ct' | xargs -r perl -p -i -e 's/([Ss])(le|el)ct/$1elect/

with only skipping net/netfilter/xt_SECMARK.c and
include/linux/netfilter/xt_SECMARK.h which have a struct member called
selctx.

Signed-off-by: Uwe Kleine-König 
Signed-off-by: Jiri Kosina

clocksource: Resume clocksource without taking the clocksource mutex

2009-09-24T20:37:53+00:00

git commit 75c5158f70c065b9 converted the clocksource spinlock to a
mutex. This causes the following BUG:

BUG: sleeping function called from invalid context at
kernel/mutex.c:280 in_atomic(): 0, irqs_disabled(): 1, pid: 2473,
name: pm-suspend 2 locks held by pm-suspend/2473:
 #0:  (&buffer->mutex){......}, at: []
sysfs_write_file+0x3c/0x137
 #1:  (pm_mutex){......}, at: []
enter_state+0x39/0x130 Pid: 2473, comm: pm-suspend Not tainted 2.6.31
#1 Call Trace:
 [] ? __debug_show_held_locks+0x22/0x24
 [] __might_sleep+0x107/0x10b
 [] mutex_lock_nested+0x25/0x43
 [] clocksource_resume+0x1c/0x60
 [] timekeeping_resume+0x1e/0x1c8
 [] __sysdev_resume+0x25/0xcf
 [] sysdev_resume+0x6d/0xae
 [] suspend_devices_and_enter+0x12b/0x1af
 [] enter_state+0xdf/0x130
 [] state_store+0xb6/0xd3
 [] kobj_attr_store+0x17/0x19
 [] sysfs_write_file+0xfb/0x137
 [] vfs_write+0xae/0x10b
 [] ? __up_read+0x1a/0x7f
 [] sys_write+0x4a/0x6e
 [] system_call_fastpath+0x16/0x1b

clocksource_resume is called early in the resume process, there is
only one cpu, no processes are running and the interrupts are
disabled. It is therefore possible to resume the clocksources
without taking the clocksource mutex.

Reported-by: Xiaotian Feng 
Signed-off-by: Martin Schwidefsky 
Tested-by: Michal Schmidt 
Cc: Xiaotian Feng 
Cc: John Stultz 
LKML-Reference: <20090924172952.49697825@mschwide.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar

clocksource: Delay clocksource down rating to late boot

2009-09-14T19:59:32+00:00

The down rating of clock sources in the early boot process via the
clock source watchdog mechanism can happen way before the per cpu
event queues are initialized. This leads to a boot crash on x86 when
the TSC is marked unstable in the SMP bring up.

The selection of a clock source for time keeping happens in the late
boot process so we can safely delay the list manipulation until
clocksource_done_booting() is called.

Signed-off-by: Thomas Gleixner 
LKML-Reference: 
Cc: Martin Schwidefsky