linux-toradex.git/Documentation/cpu-hotplug.txt, branch v3.10.78

doc: Add x86 CPU0 online/offline feature

2012-11-14T17:39:44+00:00

If CONFIG_BOOTPARAM_HOTPLUG_CPU0 is turned on, CPU0 is hotpluggable. Otherwise,
by default CPU0 is not hotpluggable and kernel parameter cpu0_hotplug enables
CPU0 online/offline feature.

The documentations point out two known CPU0 dependencies. First, resume from
hibernate or suspend always starts from CPU0. So hibernate and suspend are
prevented if CPU0 is offline. Another dependency is PIC interrupts always go
to CPU0.

It's said that some machines may depend on CPU0 to poweroff/reboot. But I
haven't seen such dependency on a few tested machines.

Please let me know if you see any CPU0 dependencies on your machine.

Signed-off-by: Fenghua Yu 
Link: http://lkml.kernel.org/r/1352835171-3958-2-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin

documentation: remove references to cpu_*_map.

2012-03-29T05:08:31+00:00

This has been obsolescent for a while, fix documentation and
misc comments.

Signed-off-by: Rusty Russell

Fix common misspellings

2011-03-31T14:26:23+00:00

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi

documentation: fix erroneous email address.

2010-08-11T13:34:10+00:00

Hey, at least it has both l's.

Reported-by: Marin Mitov 
Signed-off-by: Rusty Russell

cpumask: don't recommend set_cpus_allowed hack in Documentation/cpu-hotplug.txt

2009-12-17T01:13:29+00:00

Signed-off-by: Rusty Russell 
Cc: Gautham R Shenoy 
Cc: Ashok Raj

powerpc/pseries: Add hooks to put the CPU into an appropriate offline state

2009-11-24T03:33:04+00:00

When a CPU is offlined on POWER currently, we call rtas_stop_self() and hand
the CPU back to the resource pool. This path is used for DLPAR which will
cause a change in the LPAR configuration which will be visible outside.

This patch changes the default state a CPU is put into when it is offlined.
On platforms which support ceding the processor to the hypervisor with
latency hint specifier value, during a cpu offline operation,
instead of calling rtas_stop_self(), we cede the vCPU to the hypervisor
while passing a latency hint specifier value. The Hypervisor can use this hint
to provide better energy savings. Also, during the offline
operation, the control of the vCPU remains with the LPAR as oppposed to
returning it to the resource pool.

The patch achieves this by creating an infrastructure to set the
preferred_offline_state() which can be either
- CPU_STATE_OFFLINE: which is the current behaviour of calling
  rtas_stop_self()

- CPU_STATE_INACTIVE: which cedes the vCPU to the hypervisor with the latency
  hint specifier.

The codepath which wants to perform a DLPAR operation can set the
preferred_offline_state() of a CPU to CPU_STATE_OFFLINE before invoking
cpu_down().

The patch also provides a boot-time command line argument to disable/enable
CPU_STATE_INACTIVE.

Signed-off-by: Gautham R Shenoy 
Signed-off-by: Nathan Fontenot 
Signed-off-by: Benjamin Herrenschmidt

x86: use possible_cpus=NUM to extend the possible cpus allowed

2008-12-18T11:08:05+00:00

Impact: add new boot parameter

Use possible_cpus=NUM kernel parameter to extend the number of possible
cpus.

The ability to HOTPLUG ON cpus that are "possible" but not "present" is
dealt with in a later patch.

Signed-off-by: Mike Travis

cpu hotplug: s390 doesn't support additional_cpus anymore.

2008-08-12T23:07:28+00:00

s390 doesn't support the additional_cpus kernel parameter anymore since a
long time.  So we better update the code and documentation to reflect
that.

Cc: Martin Schwidefsky 
Signed-off-by: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[S390] Get rid of additional_cpus kernel parameter.

2008-01-26T13:11:15+00:00

It caused only a lot of confusion. From now on cpu hotplug of up to
NR_CPUS will work by default. If somebody wants to limit that then
the possible_cpus parameter can be used.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()

2008-01-25T20:08:02+00:00

Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use
get_online_cpus and put_online_cpus instead as it highlights the
refcount semantics in these operations.

The new API guarantees protection against the cpu-hotplug operation, but
it doesn't guarantee serialized access to any of the local data
structures. Hence the changes needs to be reviewed.

In case of pseries_add_processor/pseries_remove_processor, use
cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the
cpu_present_map there.

Signed-off-by: Gautham R Shenoy 
Signed-off-by: Ingo Molnar