linux-stable.git/kernel/cpu.c, branch v3.2.102

x86/smp: Don't ever patch back to UP if we unplug cpus

2018-02-13T18:32:14+00:00

commit 816afe4ff98ee10b1d30fd66361be132a0a5cee6 upstream.

We still patch SMP instructions to UP variants if we boot with a
single CPU, but not at any other time.  In particular, not if we
unplug CPUs to return to a single cpu.

Paul McKenney points out:

 mean offline overhead is 6251/48=130.2 milliseconds.

 If I remove the alternatives_smp_switch() from the offline
 path [...] the mean offline overhead is 550/42=13.1 milliseconds

Basically, we're never going to get those 120ms back, and the
code is pretty messy.

We get rid of:

 1) The "smp-alt-once" boot option. It's actually "smp-alt-boot", the
    documentation is wrong. It's now the default.

 2) The skip_smp_alternatives flag used by suspend.

 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end()
    which were only used to set this one flag.

Signed-off-by: Rusty Russell 
Cc: Paul McKenney 
Cc: Suresh Siddha 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/87vcgwwive.fsf@rustcorp.com.au
Signed-off-by: Ingo Molnar 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

hotplug: Make register and unregister notifier API symmetric

2017-03-16T02:18:29+00:00

commit 777c6e0daebb3fcefbbd6f620410a946b07ef6d0 upstream.

Yu Zhao has noticed that __unregister_cpu_notifier only unregisters its
notifiers when HOTPLUG_CPU=y while the registration might succeed even
when HOTPLUG_CPU=n if MODULE is enabled. This means that e.g. zswap
might keep a stale notifier on the list on the manual clean up during
the pool tear down and thus corrupt the list. Resulting in the following

[  144.964346] BUG: unable to handle kernel paging request at ffff880658a2be78
[  144.971337] IP: [] raw_notifier_chain_register+0x1b/0x40

[  145.122628] Call Trace:
[  145.125086]  [] __register_cpu_notifier+0x18/0x20
[  145.131350]  [] zswap_pool_create+0x273/0x400
[  145.137268]  [] __zswap_param_set+0x1fc/0x300
[  145.143188]  [] ? trace_hardirqs_on+0xd/0x10
[  145.149018]  [] ? kernel_param_lock+0x28/0x30
[  145.154940]  [] ? __might_fault+0x4f/0xa0
[  145.160511]  [] zswap_compressor_param_set+0x17/0x20
[  145.167035]  [] param_attr_store+0x5c/0xb0
[  145.172694]  [] module_attr_store+0x1d/0x30
[  145.178443]  [] sysfs_kf_write+0x4f/0x70
[  145.183925]  [] kernfs_fop_write+0x149/0x180
[  145.189761]  [] __vfs_write+0x18/0x40
[  145.194982]  [] vfs_write+0xb2/0x1a0
[  145.200122]  [] SyS_write+0x52/0xa0
[  145.205177]  [] entry_SYSCALL_64_fastpath+0x12/0x17

This can be even triggered manually by changing
/sys/module/zswap/parameters/compressor multiple times.

Fix this issue by making unregister APIs symmetric to the register so
there are no surprises.

Fixes: 47e627bc8c9a ("[PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU")
Reported-and-tested-by: Yu Zhao 
Signed-off-by: Michal Hocko 
Cc: linux-mm@kvack.org
Cc: Andrew Morton 
Cc: Dan Streetman 
Link: http://lkml.kernel.org/r/20161207135438.4310-1-mhocko@kernel.org
Signed-off-by: Thomas Gleixner 
[bwh: Backported to 3.2:
 - The lockless (__-prefixed) variants don't exist
 - Keep definition of cpu_notify_nofail() conditional on CONFIG_HOTPLUG_CPU]
Signed-off-by: Ben Hutchings

CPU hotplug: provide a generic helper to disable/enable CPU hotplug

2013-06-19T01:16:59+00:00

commit 16e53dbf10a2d7e228709a7286310e629ede5e45 upstream.

There are instances in the kernel where we would like to disable CPU
hotplug (from sysfs) during some important operation.  Today the freezer
code depends on this and the code to do it was kinda tailor-made for
that.

Restructure the code and make it generic enough to be useful for other
usecases too.

Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: Robin Holt 
Cc: H. Peter Anvin 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Russ Anderson 
Cc: Robin Holt 
Cc: Russell King 
Cc: Guan Xuetao 
Cc: Shawn Guo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux

2011-11-07T03:44:47+00:00

* 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: (230 commits)
  Revert "tracing: Include module.h in define_trace.h"
  irq: don't put module.h into irq.h for tracking irqgen modules.
  bluetooth: macroize two small inlines to avoid module.h
  ip_vs.h: fix implicit use of module_get/module_put from module.h
  nf_conntrack.h: fix up fallout from implicit moduleparam.h presence
  include: replace linux/module.h with "struct module" wherever possible
  include: convert various register fcns to macros to avoid include chaining
  crypto.h: remove unused crypto_tfm_alg_modname() inline
  uwb.h: fix implicit use of asm/page.h for PAGE_SIZE
  pm_runtime.h: explicitly requires notifier.h
  linux/dmaengine.h: fix implicit use of bitmap.h and asm/page.h
  miscdevice.h: fix up implicit use of lists and types
  stop_machine.h: fix implicit use of smp.h for smp_processor_id
  of: fix implicit use of errno.h in include/linux/of.h
  of_platform.h: delete needless include 
  acpi: remove module.h include from platform/aclinux.h
  miscdevice.h: delete unnecessary inclusion of module.h
  device_cgroup.h: delete needless include 
  net: sch_generic remove redundant use of 
  net: inet_timewait_sock doesnt need 
  ...

Fix up trivial conflicts (other header files, and  removal of the ab3550 mfd driver) in
 - drivers/media/dvb/frontends/dibx000_common.c
 - drivers/media/video/{mt9m111.c,ov6650.c}
 - drivers/mfd/ab3550-core.c
 - include/linux/dmaengine.h

PM / Sleep: Fix race between CPU hotplug and freezer

2011-11-04T21:28:09+00:00

The CPU hotplug notifications sent out by the _cpu_up() and _cpu_down()
functions depend on the value of the 'tasks_frozen' argument passed to them
(which indicates whether tasks have been frozen or not).
(Examples for such CPU hotplug notifications: CPU_ONLINE, CPU_ONLINE_FROZEN,
CPU_DEAD, CPU_DEAD_FROZEN).

Thus, it is essential that while the callbacks for those notifications are
running, the state of the system with respect to the tasks being frozen or
not remains unchanged, *throughout that duration*. Hence there is a need for
synchronizing the CPU hotplug code with the freezer subsystem.

Since the freezer is involved only in the Suspend/Hibernate call paths, this
patch hooks the CPU hotplug code to the suspend/hibernate notifiers
PM_[SUSPEND|HIBERNATE]_PREPARE and PM_POST_[SUSPEND|HIBERNATE] to prevent
the race between CPU hotplug and freezer, thus ensuring that CPU hotplug
notifications will always be run with the state of the system really being
what the notifications indicate, _throughout_ their execution time.

Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: Rafael J. Wysocki

kernel: Map most files to use export.h instead of module.h

2011-10-31T13:20:12+00:00

The changed files were only including linux/module.h for the
EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
onto the isolated export header for faster compile times.

Nothing to see here but a whole lot of instances of:

  -#include 
  +#include 

This commit is only changing the kernel dir; next targets
will probably be mm, fs, the arch dirs, etc.

Signed-off-by: Paul Gortmaker

Fix common misspellings

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

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi

kernel/cpu.c: fix many errors related to style.

2011-03-23T00:44:11+00:00

Change the printk() calls to have the KERN_INFO/KERN_ERROR stuff, and
fixes other coding style errors.  Not _all_ of them are gone, though.

[akpm@linux-foundation.org: revert the bits I disagree with]
Signed-off-by: Michael Rodriguez 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branches 'x86-alternatives-for-linus', 'x86-fpu-for-linus', 'x86-hwmon-for-linus', 'x86-paravirt-for-linus', 'core-locking-for-linus' and 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-01-06T19:11:50+00:00

* 'x86-alternatives-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, suspend: Avoid unnecessary smp alternatives switch during suspend/resume

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86-64, asm: Use fxsaveq/fxrestorq in more places

* 'x86-hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, hwmon: Add core threshold notification to therm_throt.c

* 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, paravirt: Use native_halt on a halt, not native_safe_halt

* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  locking, lockdep: Convert sprintf_symbol to %pS

* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  irq: Better struct irqaction layout

x86, suspend: Avoid unnecessary smp alternatives switch during suspend/resume

2010-12-14T00:23:56+00:00

During suspend, we disable all the non boot cpus. And during resume we bring
them all back again. So no need to do alternatives_smp_switch() in between.

On my core 2 based laptop, this speeds up the suspend path by 15msec and the
resume path by 5 msec (suspend/resume speed up differences can be attributed
to the different P-states that the cpu is in during suspend/resume).

Signed-off-by: Suresh Siddha 
LKML-Reference: <1290557500.4946.8.camel@sbsiddha-MOBL3.sc.intel.com>
Cc: Rafael J. Wysocki 
Signed-off-by: H. Peter Anvin