Add user_reserve_kbytes knob.

Limit the growth of the memory reserved for other user processes to
min(3% current process size, user_reserve_pages).  Only about 8MB is
necessary to enable recovery in the default mode, and only a few hundred
MB are required even when overcommit is disabled.

user_reserve_pages defaults to min(3% free pages, 128MB)

I arrived at 128MB by taking the max VSZ of sshd, login, bash, and top ...
then adding the RSS of each.

This only affects OVERCOMMIT_NEVER mode.

Background

1. user reserve

__vm_enough_memory reserves a hardcoded 3% of the current process size for
other applications when overcommit is disabled.  This was done so that a
user could recover if they launched a memory hogging process.  Without the
reserve, a user would easily run into a message such as:

bash: fork: Cannot allocate memory

2. admin reserve

Additionally, a hardcoded 3% of free memory is reserved for root in both
overcommit 'guess' and 'never' modes.  This was intended to prevent a
scenario where root-cant-log-in and perform recovery operations.

Note that this reserve shrinks, and doesn't guarantee a useful reserve.

Motivation

The two hardcoded memory reserves should be updated to account for current
memory sizes.

Also, the admin reserve would be more useful if it didn't shrink too much.

When the current code was originally written, 1GB was considered
"enterprise".  Now the 3% reserve can grow to multiple GB on large memory
systems, and it only needs to be a few hundred MB at most to enable a user
or admin to recover a system with an unwanted memory hogging process.

I've found that reducing these reserves is especially beneficial for a
specific type of application load:

 * single application system
 * one or few processes (e.g. one per core)
 * allocating all available memory
 * not initializing every page immediately
 * long running

I've run scientific clusters with this sort of load.  A long running job
sometimes failed many hours (weeks of CPU time) into a calculation.  They
weren't initializing all of their memory immediately, and they weren't
using calloc, so I put systems into overcommit 'never' mode.  These
clusters run diskless and have no swap.

However, with the current reserves, a user wishing to allocate as much
memory as possible to one process may be prevented from using, for
example, almost 2GB out of 32GB.

The effect is less, but still significant when a user starts a job with
one process per core.  I have repeatedly seen a set of processes
requesting the same amount of memory fail because one of them could not
allocate the amount of memory a user would expect to be able to allocate.
For example, Message Passing Interfce (MPI) processes, one per core.  And
it is similar for other parallel programming frameworks.

Changing this reserve code will make the overcommit never mode more useful
by allowing applications to allocate nearly all of the available memory.

Also, the new admin_reserve_kbytes will be safer than the current behavior
since the hardcoded 3% of available memory reserve can shrink to something
useless in the case where applications have grabbed all available memory.

Risks

* "bash: fork: Cannot allocate memory"

  The downside of the first patch-- which creates a tunable user reserve
  that is only used in overcommit 'never' mode--is that an admin can set
  it so low that a user may not be able to kill their process, even if
  they already have a shell prompt.

  Of course, a user can get in the same predicament with the current 3%
  reserve--they just have to launch processes until 3% becomes negligible.

* root-cant-log-in problem

  The second patch, adding the tunable rootuser_reserve_pages, allows
  the admin to shoot themselves in the foot by setting it too small.  They
  can easily get the system into a state where root-can't-log-in.

  However, the new admin_reserve_kbytes will be safer than the current
  behavior since the hardcoded 3% of available memory reserve can shrink
  to something useless in the case where applications have grabbed all
  available memory.

Alternatives

 * Memory cgroups provide a more flexible way to limit application memory.

   Not everyone wants to set up cgroups or deal with their overhead.

 * We could create a fourth overcommit mode which provides smaller reserves.

   The size of useful reserves may be drastically different depending
   on the whether the system is embedded or enterprise.

 * Force users to initialize all of their memory or use calloc.

   Some users don't want/expect the system to overcommit when they malloc.
   Overcommit 'never' mode is for this scenario, and it should work well.

The new user and admin reserve tunables are simple to use, with low
overhead compared to cgroups.  The patches preserve current behavior where
3% of memory is less than 128MB, except that the admin reserve doesn't
shrink to an unusable size under pressure.  The code allows admins to tune
for embedded and enterprise usage.

FAQ

 * How is the root-cant-login problem addressed?
   What happens if admin_reserve_pages is set to 0?

   Root is free to shoot themselves in the foot by setting
   admin_reserve_kbytes too low.

   On x86_64, the minimum useful reserve is:
     8MB for overcommit 'guess'
   128MB for overcommit 'never'

   admin_reserve_pages defaults to min(3% free memory, 8MB)

   So, anyone switching to 'never' mode needs to adjust
   admin_reserve_pages.

 * How do you calculate a minimum useful reserve?

   A user or the admin needs enough memory to login and perform
   recovery operations, which includes, at a minimum:

   sshd or login + bash (or some other shell) + top (or ps, kill, etc.)

   For overcommit 'guess', we can sum resident set sizes (RSS)
   because we only need enough memory to handle what the recovery
   programs will typically use. On x86_64 this is about 8MB.

   For overcommit 'never', we can take the max of their virtual sizes (VSZ)
   and add the sum of their RSS. We use VSZ instead of RSS because mode
   forces us to ensure we can fulfill all of the requested memory allocations--
   even if the programs only use a fraction of what they ask for.
   On x86_64 this is about 128MB.

   When swap is enabled, reserves are useful even when they are as
   small as 10MB, regardless of overcommit mode.

   When both swap and overcommit are disabled, then the admin should
   tune the reserves higher to be absolutley safe. Over 230MB each
   was safest in my testing.

 * What happens if user_reserve_pages is set to 0?

   Note, this only affects overcomitt 'never' mode.

   Then a user will be able to allocate all available memory minus
   admin_reserve_kbytes.

   However, they will easily see a message such as:

   "bash: fork: Cannot allocate memory"

   And they won't be able to recover/kill their application.
   The admin should be able to recover the system if
   admin_reserve_kbytes is set appropriately.

 * What's the difference between overcommit 'guess' and 'never'?

   "Guess" allows an allocation if there are enough free + reclaimable
   pages. It has a hardcoded 3% of free pages reserved for root.

   "Never" allows an allocation if there is enough swap + a configurable
   percentage (default is 50) of physical RAM. It has a hardcoded 3% of
   free pages reserved for root, like "Guess" mode. It also has a
   hardcoded 3% of the current process size reserved for additional
   applications.

 * Why is overcommit 'guess' not suitable even when an app eventually
   writes to every page? It takes free pages, file pages, available
   swap pages, reclaimable slab pages into consideration. In other words,
   these are all pages available, then why isn't overcommit suitable?

   Because it only looks at the present state of the system. It
   does not take into account the memory that other applications have
   malloced, but haven't initialized yet. It overcommits the system.

Test Summary

There was little change in behavior in the default overcommit 'guess'
mode with swap enabled before and after the patch. This was expected.

Systems run most predictably (i.e. no oom kills) in overcommit 'never'
mode with swap enabled. This also allowed the most memory to be allocated
to a user application.

Overcommit 'guess' mode without swap is a bad idea. It is easy to
crash the system. None of the other tested combinations crashed.
This matches my experience on the Roadrunner supercomputer.

Without the tunable user reserve, a system in overcommit 'never' mode
and without swap does not allow the admin to recover, although the
admin can.

With the new tunable reserves, a system in overcommit 'never' mode
and without swap can be configured to:

1. maximize user-allocatable memory, running close to the edge of
recoverability

2. maximize recoverability, sacrificing allocatable memory to
ensure that a user cannot take down a system

Test Description

Fedora 18 VM - 4 x86_64 cores, 5725MB RAM, 4GB Swap

System is booted into multiuser console mode, with unnecessary services
turned off. Caches were dropped before each test.

Hogs are user memtester processes that attempt to allocate all free memory
as reported by /proc/meminfo

In overcommit 'never' mode, memory_ratio=100

Test Results

3.9.0-rc1-mm1

Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
----------   ----   ----   -------------   ----   -------------   --------------
guess        yes    1      5432/5432       no     yes             yes
guess        yes    4      5444/5444       1      yes             yes
guess        no     1      5302/5449       no     yes             yes
guess        no     4      -               crash  no              no

never        yes    1      5460/5460       1      yes             yes
never        yes    4      5460/5460       1      yes             yes
never        no     1      5218/5432       no     no              yes
never        no     4      5203/5448       no     no              yes

3.9.0-rc1-mm1-tunablereserves

User and Admin Recovery show their respective reserves, if applicable.

Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
----------   ----   ----   -------------   ----   -------------   --------------
guess        yes    1      5419/5419       no     - yes           8MB yes
guess        yes    4      5436/5436       1      - yes           8MB yes
guess        no     1      5440/5440       *      - yes           8MB yes
guess        no     4      -               crash  - no            8MB no

* process would successfully mlock, then the oom killer would pick it

never        yes    1      5446/5446       no     10MB yes        20MB yes
never        yes    4      5456/5456       no     10MB yes        20MB yes
never        no     1      5387/5429       no     128MB no        8MB barely
never        no     1      5323/5428       no     226MB barely    8MB barely
never        no     1      5323/5428       no     226MB barely    8MB barely

never        no     1      5359/5448       no     10MB no         10MB barely

never        no     1      5323/5428       no     0MB no          10MB barely
never        no     1      5332/5428       no     0MB no          50MB yes
never        no     1      5293/5429       no     0MB no          90MB yes

never        no     1      5001/5427       no     230MB yes       338MB yes
never        no     4*     4998/5424       no     230MB yes       338MB yes

* more memtesters were launched, able to allocate approximately another 100MB

Future Work

 - Test larger memory systems.

 - Test an embedded image.

 - Test other architectures.

 - Time malloc microbenchmarks.

 - Would it be useful to be able to set overcommit policy for
   each memory cgroup?

 - Some lines are slightly above 80 chars.
   Perhaps define a macro to convert between pages and kb?
   Other places in the kernel do this.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: make init_user_reserve() static]
Signed-off-by: NAndrew Shewmaker <agshew@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use the new interface, remove one ifdef.  No code size changes.

We could/should have been using __meminit/__meminitdata here but there's
now no point in doing that because all this code is elided at compile time.

Cc: Li Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now, vmap_area_list is exported as VMCOREINFO for makedumpfile to get
the start address of vmalloc region (vmalloc_start).  The address which
contains vmalloc_start value is represented as below:

  vmap_area_list.next - OFFSET(vmap_area.list) + OFFSET(vmap_area.va_start)

However, both OFFSET(vmap_area.va_start) and OFFSET(vmap_area.list)
aren't exported as VMCOREINFO.

So this patch exports them externally with small cleanup.

[akpm@linux-foundation.org: vmalloc.h should include list.h for list_head]
Signed-off-by: NAtsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Although our intention is to unexport internal structure entirely, but
there is one exception for kexec.  kexec dumps address of vmlist and
makedumpfile uses this information.

We are about to remove vmlist, then another way to retrieve information
of vmalloc layer is needed for makedumpfile.  For this purpose, we
export vmap_area_list, instead of vmlist.
Signed-off-by: NJoonsoo Kim <js1304@gmail.com>
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drop_caches.c provides code only invokable via sysctl, so don't compile it
in when CONFIG_SYSCTL=n.
Signed-off-by: NJosh Triplett <josh@joshtriplett.org>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that we have generic and well ordered cgroup tree walkers there is
no need to keep css_get_next in the place.
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NLi Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use common help functions to free reserved pages.
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

audit_trim_trees() calls get_tree().  If a failure occurs we must call
put_tree().

[akpm@linux-foundation.org: run put_tree() before mutex_lock() for small scalability improvement]
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In audit_data_to_entry() when a failure occurs we must check and free
the tree and watch to avoid a memory leak.

  test:
    plan:
      test command:
        "auditctl -a exit,always -w /etc -F auid=-1"
        (on fedora17, need modify auditctl to let "-w /etc" has effect)
      running:
        under fedora17 x86_64, 2 CPUs 3.20GHz, 2.5GB RAM.
        let 15 auditctl processes continue running at the same time.
      monitor command:
        watch -d -n 1 "cat /proc/meminfo | awk '{print \$2}' \
          | head -n 4 | xargs \
          | awk '{print \"used \",\$1 - \$2 - \$3 - \$4}'"

    result:
      for original version:
        will use up all memory, within 3 hours.
        kill all auditctl, the memory still does not free.
      for new version (apply this patch):
        after 14 hours later, not find issues.
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The files which include kernel/audit.h are complied only when
CONFIG_AUDIT is set.

Just like audit_pid, there is no need to surround audit_ever_enabled
with CONFIG_AUDIT.
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

audit_enabled has already been exported in include/linux/audit.h.  and
kernel/audit.h includes include/linux/audit.h, no need to export
aduit_enabled again in kernel/audit.h
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We only need to check if kauditd is valid after we start it, if kauditd
is invalid, we will set kauditd_task to NULL.  So next time, we will
start kauditd again.

It means if kauditd_task is not NULL,it must be valid.
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In audit_alloc_context() use kzalloc instead of kmalloc+memset.  Also
rename audit_zero_context() to audit_set_context(), to represent it's
inner workings properly.

[akpm@linux-foundation.org: remove audit_set_context() altogether - fold it into its caller]
Signed-off-by: NRakib Mullick <rakib.mullick@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

task_get_live_kthread() looks confusing and unneeded.  It does
get_task_struct() but only kthread_stop() needs this, it can be called
even if the calller doesn't have a reference when we know that this
kthread can't exit until we do kthread_stop().

kthread_park() and kthread_unpark() do not need get_task_struct(), the
callers already have the reference.  And it can not help if we can race
with the exiting kthread anyway, kthread_park() can hang forever in this
case.

Change kthread_park() and kthread_unpark() to use to_live_kthread(),
change kthread_stop() to do get_task_struct() by hand and remove
task_get_live_kthread().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

"k->vfork_done != NULL" with a barrier() after to_kthread(k) in
task_get_live_kthread(k) looks unclear, and sub-optimal because we load
->vfork_done twice.

All we need is to ensure that we do not return to_kthread(NULL).  Add a
new trivial helper which loads/checks ->vfork_done once, this also looks
more understandable.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Also add some missing printk levels.
Signed-off-by: NDave Jones <davej@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20130425174002.GA26769@redhat.com
[ Tweaked the messages a bit. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

We occasionally get reports of these BUGs being hit, and the
stack trace doesn't necessarily always tell us what we need to
know about why we are hitting those limits.

If users start attaching /proc/lock_stats to reports we may have
more of a clue what's going on.
Signed-off-by: NDave Jones <davej@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20130423163403.GA12839@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The following RCU splat indicates lack of RCU protection:

[  953.267649] ===============================
[  953.267652] [ INFO: suspicious RCU usage. ]
[  953.267657] 3.9.0-0.rc6.git2.4.fc19.ppc64p7 #1 Not tainted
[  953.267661] -------------------------------
[  953.267664] include/linux/cgroup.h:534 suspicious rcu_dereference_check() usage!
[  953.267669]
[  953.267669] other info that might help us debug this:
[  953.267669]
[  953.267675]
[  953.267675] rcu_scheduler_active = 1, debug_locks = 0
[  953.267680] 1 lock held by glxgears/1289:
[  953.267683]  #0:  (&sig->cred_guard_mutex){+.+.+.}, at: [<c00000000027f884>] .prepare_bprm_creds+0x34/0xa0
[  953.267700]
[  953.267700] stack backtrace:
[  953.267704] Call Trace:
[  953.267709] [c0000001f0d1b6e0] [c000000000016e30] .show_stack+0x130/0x200 (unreliable)
[  953.267717] [c0000001f0d1b7b0] [c0000000001267f8] .lockdep_rcu_suspicious+0x138/0x180
[  953.267724] [c0000001f0d1b840] [c0000000001d43a4] .perf_event_comm+0x4c4/0x690
[  953.267731] [c0000001f0d1b950] [c00000000027f6e4] .set_task_comm+0x84/0x1f0
[  953.267737] [c0000001f0d1b9f0] [c000000000280414] .setup_new_exec+0x94/0x220
[  953.267744] [c0000001f0d1ba70] [c0000000002f665c] .load_elf_binary+0x58c/0x19b0
...

This commit therefore adds the required RCU read-side critical
section to perf_event_comm().
Reported-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: a.p.zijlstra@chello.nl
Cc: paulus@samba.org
Cc: acme@ghostprotocols.net
Link: http://lkml.kernel.org/r/20130419190124.GA8638@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
Tested-by: NGustavo Luiz Duarte <gusld@br.ibm.com>

Linus suggested that probably all the supported architectures can
allow a negative mutex count without incorrect behavior, so we can
then back out the architecture specific change and allow the
mutex count to go to any negative number. That should further
reduce contention for non-x86 architecture.
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NWaiman Long <Waiman.Long@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Norton Scott J <scott.norton@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-5-git-send-email-Waiman.Long@hp.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

The current mutex spinning code (with MUTEX_SPIN_ON_OWNER option
turned on) allow multiple tasks to spin on a single mutex
concurrently. A potential problem with the current approach is
that when the mutex becomes available, all the spinning tasks
will try to acquire the mutex more or less simultaneously. As a
result, there will be a lot of cacheline bouncing especially on
systems with a large number of CPUs.

This patch tries to reduce this kind of contention by putting
the mutex spinners into a queue so that only the first one in
the queue will try to acquire the mutex. This will reduce
contention and allow all the tasks to move forward faster.

The queuing of mutex spinners is done using an MCS lock based
implementation which will further reduce contention on the mutex
cacheline than a similar ticket spinlock based implementation.
This patch will add a new field into the mutex data structure
for holding the MCS lock. This expands the mutex size by 8 bytes
for 64-bit system and 4 bytes for 32-bit system. This overhead
will be avoid if the MUTEX_SPIN_ON_OWNER option is turned off.

The following table shows the jobs per minute (JPM) scalability
data on an 8-node 80-core Westmere box with a 3.7.10 kernel. The
numactl command is used to restrict the running of the fserver
workloads to 1/2/4/8 nodes with hyperthreading off.

+-----------------+-----------+-----------+-------------+----------+
|  Configuration  | Mean JPM  | Mean JPM  |  Mean JPM   | % Change |
|                 | w/o patch | patch 1   | patches 1&2 |  1->1&2  |
+-----------------+------------------------------------------------+
|                 |              User Range 1100 - 2000            |
+-----------------+------------------------------------------------+
| 8 nodes, HT off |  227972   |  227237   |   305043    |  +34.2%  |
| 4 nodes, HT off |  393503   |  381558   |   394650    |   +3.4%  |
| 2 nodes, HT off |  334957   |  325240   |   338853    |   +4.2%  |
| 1 node , HT off |  198141   |  197972   |   198075    |   +0.1%  |
+-----------------+------------------------------------------------+
|                 |              User Range 200 - 1000             |
+-----------------+------------------------------------------------+
| 8 nodes, HT off |  282325   |  312870   |   332185    |   +6.2%  |
| 4 nodes, HT off |  390698   |  378279   |   393419    |   +4.0%  |
| 2 nodes, HT off |  336986   |  326543   |   340260    |   +4.2%  |
| 1 node , HT off |  197588   |  197622   |   197582    |    0.0%  |
+-----------------+-----------+-----------+-------------+----------+

At low user range 10-100, the JPM differences were within +/-1%.
So they are not that interesting.

The fserver workload uses mutex spinning extensively. With just
the mutex change in the first patch, there is no noticeable
change in performance.  Rather, there is a slight drop in
performance. This mutex spinning patch more than recovers the
lost performance and show a significant increase of +30% at high
user load with the full 8 nodes. Similar improvements were also
seen in a 3.8 kernel.

The table below shows the %time spent by different kernel
functions as reported by perf when running the fserver workload
at 1500 users with all 8 nodes.

+-----------------------+-----------+---------+-------------+
|        Function       |  % time   | % time  |   % time    |
|                       | w/o patch | patch 1 | patches 1&2 |
+-----------------------+-----------+---------+-------------+
| __read_lock_failed    |  34.96%   | 34.91%  |   29.14%    |
| __write_lock_failed   |  10.14%   | 10.68%  |    7.51%    |
| mutex_spin_on_owner   |   3.62%   |  3.42%  |    2.33%    |
| mspin_lock            |    N/A    |   N/A   |    9.90%    |
| __mutex_lock_slowpath |   1.46%   |  0.81%  |    0.14%    |
| _raw_spin_lock        |   2.25%   |  2.50%  |    1.10%    |
+-----------------------+-----------+---------+-------------+

The fserver workload for an 8-node system is dominated by the
contention in the read/write lock. Mutex contention also plays a
role. With the first patch only, mutex contention is down (as
shown by the __mutex_lock_slowpath figure) which help a little
bit. We saw only a few percents improvement with that.

By applying patch 2 as well, the single mutex_spin_on_owner
figure is now split out into an additional mspin_lock figure.
The time increases from 3.42% to 11.23%. It shows a great
reduction in contention among the spinners leading to a 30%
improvement. The time ratio 9.9/2.33=4.3 indicates that there
are on average 4+ spinners waiting in the spin_lock loop for
each spinner in the mutex_spin_on_owner loop. Contention in
other locking functions also go down by quite a lot.

The table below shows the performance change of both patches 1 &
2 over patch 1 alone in other AIM7 workloads (at 8 nodes,
hyperthreading off).

+--------------+---------------+----------------+-----------------+
|   Workload   | mean % change | mean % change  | mean % change   |
|              | 10-100 users  | 200-1000 users | 1100-2000 users |
+--------------+---------------+----------------+-----------------+
| alltests     |      0.0%     |     -0.8%      |     +0.6%       |
| five_sec     |     -0.3%     |     +0.8%      |     +0.8%       |
| high_systime |     +0.4%     |     +2.4%      |     +2.1%       |
| new_fserver  |     +0.1%     |    +14.1%      |    +34.2%       |
| shared       |     -0.5%     |     -0.3%      |     -0.4%       |
| short        |     -1.7%     |     -9.8%      |     -8.3%       |
+--------------+---------------+----------------+-----------------+

The short workload is the only one that shows a decline in
performance probably due to the spinner locking and queuing
overhead.
Signed-off-by: NWaiman Long <Waiman.Long@hp.com>
Reviewed-by: NDavidlohr Bueso <davidlohr.bueso@hp.com>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Norton Scott J <scott.norton@hp.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-4-git-send-email-Waiman.Long@hp.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

In the __mutex_lock_common() function, an initial entry into
the lock slow path will cause two atomic_xchg instructions to be
issued. Together with the atomic decrement in the fast path, a
total of three atomic read-modify-write instructions will be
issued in rapid succession. This can cause a lot of cache
bouncing when many tasks are trying to acquire the mutex at the
same time.

This patch will reduce the number of atomic_xchg instructions
used by checking the counter value first before issuing the
instruction. The atomic_read() function is just a simple memory
read. The atomic_xchg() function, on the other hand, can be up
to 2 order of magnitude or even more in cost when compared with
atomic_read(). By using atomic_read() to check the value first
before calling atomic_xchg(), we can avoid a lot of unnecessary
cache coherency traffic. The only downside with this change is
that a task on the slow path will have a tiny bit less chance of
getting the mutex when competing with another task in the fast
path.

The same is true for the atomic_cmpxchg() function in the
mutex-spin-on-owner loop. So an atomic_read() is also performed
before calling atomic_cmpxchg().

The mutex locking and unlocking code for the x86 architecture
can allow any negative number to be used in the mutex count to
indicate that some tasks are waiting for the mutex. I am not so
sure if that is the case for the other architectures. So the
default is to avoid atomic_xchg() if the count has already been
set to -1. For x86, the check is modified to include all
negative numbers to cover a larger case.

The following table shows the jobs per minutes (JPM) scalability
data on an 8-node 80-core Westmere box with a 3.7.10 kernel. The
numactl command is used to restrict the running of the
high_systime workloads to 1/2/4/8 nodes with hyperthreading on
and off.

+-----------------+-----------+------------+----------+
|  Configuration  | Mean JPM  |  Mean JPM  | % Change |
|		  | w/o patch | with patch |	      |
+-----------------+-----------------------------------+
|		  |      User Range 1100 - 2000	      |
+-----------------+-----------------------------------+
| 8 nodes, HT on  |    36980   |   148590  | +301.8%  |
| 8 nodes, HT off |    42799   |   145011  | +238.8%  |
| 4 nodes, HT on  |    61318   |   118445  |  +51.1%  |
| 4 nodes, HT off |   158481   |   158592  |   +0.1%  |
| 2 nodes, HT on  |   180602   |   173967  |   -3.7%  |
| 2 nodes, HT off |   198409   |   198073  |   -0.2%  |
| 1 node , HT on  |   149042   |   147671  |   -0.9%  |
| 1 node , HT off |   126036   |   126533  |   +0.4%  |
+-----------------+-----------------------------------+
|		  |       User Range 200 - 1000	      |
+-----------------+-----------------------------------+
| 8 nodes, HT on  |   41525    |   122349  | +194.6%  |
| 8 nodes, HT off |   49866    |   124032  | +148.7%  |
| 4 nodes, HT on  |   66409    |   106984  |  +61.1%  |
| 4 nodes, HT off |  119880    |   130508  |   +8.9%  |
| 2 nodes, HT on  |  138003    |   133948  |   -2.9%  |
| 2 nodes, HT off |  132792    |   131997  |   -0.6%  |
| 1 node , HT on  |  116593    |   115859  |   -0.6%  |
| 1 node , HT off |  104499    |   104597  |   +0.1%  |
+-----------------+------------+-----------+----------+

At low user range 10-100, the JPM differences were within +/-1%.
So they are not that interesting.

AIM7 benchmark run has a pretty large run-to-run variance due to
random nature of the subtests executed. So a difference of less
than +-5% may not be really significant.

This patch improves high_systime workload performance at 4 nodes
and up by maintaining transaction rates without significant
drop-off at high node count.  The patch has practically no
impact on 1 and 2 nodes system.

The table below shows the percentage time (as reported by perf
record -a -s -g) spent on the __mutex_lock_slowpath() function
by the high_systime workload at 1500 users for 2/4/8-node
configurations with hyperthreading off.

+---------------+-----------------+------------------+---------+
| Configuration | %Time w/o patch | %Time with patch | %Change |
+---------------+-----------------+------------------+---------+
|    8 nodes    |      65.34%     |      0.69%       |  -99%   |
|    4 nodes    |       8.70%	  |      1.02%	     |  -88%   |
|    2 nodes    |       0.41%     |      0.32%       |  -22%   |
+---------------+-----------------+------------------+---------+

It is obvious that the dramatic performance improvement at 8
nodes was due to the drastic cut in the time spent within the
__mutex_lock_slowpath() function.

The table below show the improvements in other AIM7 workloads
(at 8 nodes, hyperthreading off).

+--------------+---------------+----------------+-----------------+
|   Workload   | mean % change | mean % change  | mean % change   |
|              | 10-100 users  | 200-1000 users | 1100-2000 users |
+--------------+---------------+----------------+-----------------+
| alltests     |     +0.6%     |   +104.2%      |   +185.9%       |
| five_sec     |     +1.9%     |     +0.9%      |     +0.9%       |
| fserver      |     +1.4%     |     -7.7%      |     +5.1%       |
| new_fserver  |     -0.5%     |     +3.2%      |     +3.1%       |
| shared       |    +13.1%     |   +146.1%      |   +181.5%       |
| short        |     +7.4%     |     +5.0%      |     +4.2%       |
+--------------+---------------+----------------+-----------------+
Signed-off-by: NWaiman Long <Waiman.Long@hp.com>
Reviewed-by: NDavidlohr Bueso <davidlohr.bueso@hp.com>
Reviewed-by: NRik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Norton: Scott J <scott.norton@hp.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-3-git-send-email-Waiman.Long@hp.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

As mentioned by Ingo, the SCHED_FEAT_OWNER_SPIN scheduler
feature bit was really just an early hack to make with/without
mutex-spinning testable. So it is no longer necessary.

This patch removes the SCHED_FEAT_OWNER_SPIN feature bit and
move the mutex spinning code from kernel/sched/core.c back to
kernel/mutex.c which is where they should belong.
Signed-off-by: NWaiman Long <Waiman.Long@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chandramouleeswaran Aswin <aswin@hp.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Norton Scott J <scott.norton@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1366226594-5506-2-git-send-email-Waiman.Long@hp.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This reverts commit 3a366e61.

Wanlong Gao reports that it causes a kernel panic on his machine several
minutes after boot. Reverting it removes the panic.

Jens says:
 "It's not quite clear why that is yet, so I think we should just revert
  the commit for 3.9 final (which I'm assuming is pretty close).

  The wifi is crap at the LSF hotel, so sending this email instead of
  queueing up a revert and pull request."
Reported-by: NWanlong Gao <gaowanlong@cn.fujitsu.com>
Requested-by: NJens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix a double locking bug caused when debug.kprobe-optimization=0.
While the proc_kprobes_optimization_handler locks kprobe_mutex,
wait_for_kprobe_optimizer locks it again and that causes a double lock.
To fix the bug, this introduces different mutex for protecting
sysctl parameter and locks it in proc_kprobes_optimization_handler.
Of course, since we need to lock kprobe_mutex when touching kprobes
resources, that is done in *optimize_all_kprobes().

This bug was introduced by commit ad72b3be ("kprobes: fix
wait_for_kprobe_optimizer()")
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This fixes a kernel memory contents leak via the tkill and tgkill syscalls
for compat processes.

This is visible in the siginfo_t->_sifields._rt.si_sigval.sival_ptr field
when handling signals delivered from tkill.

The place of the infoleak:

int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
{
        ...
        put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
        ...
}
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
Reviewed-by: NPaX Team <pageexec@freemail.hu>
Signed-off-by: NKees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We can extend kexec-tools to support multiple "Crash kernel" in /proc/iomem
instead.

So we can use "Crash kernel" instead of "Crash kernel low" in /proc/iomem.
Suggested-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1366089828-19692-3-git-send-email-yinghai@kernel.orgAcked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Per hpa, use crashkernel=X,high crashkernel=Y,low instead of
crashkernel_hign=X crashkernel_low=Y. As that could be extensible.

-v2: according to Vivek, change delimiter to ;
-v3: let hign and low only handle simple form and it conforms to
	description in kernel-parameters.txt
     still keep crashkernel=X override any crashkernel=X,high
        crashkernel=Y,low
-v4: update get_last_crashkernel returning and add more strict
     checking in parse_crashkernel_simple() found by HATAYAMA.
-v5: Change delimiter back to , according to HPA.
     also separate parse_suffix from parse_simper according to vivek.
	so we can avoid @pos in that path.
-v6: Tight the checking about crashkernel=X,highblahblah,high
     found by HTYAYAMA.

Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1366089828-19692-5-git-send-email-yinghai@kernel.orgAcked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Vivek found old kexec-tools does not work new kernel anymore.

So change back crashkernel= back to old behavoir, and add crashkernel_high=
to let user decide if buffer could be above 4G, and also new kexec-tools will
be needed.

-v2: let crashkernel=X override crashkernel_high=
    update description about _high will be ignored by crashkernel=X
-v3: update description about kernel-parameters.txt according to Vivek.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1366089828-19692-4-git-send-email-yinghai@kernel.orgAcked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Trinity discovered that we fail to check all 64 bits of
attr.config passed by user space, resulting to out-of-bounds
access of the perf_swevent_enabled array in
sw_perf_event_destroy().

Introduced in commit b0a873eb ("perf: Register PMU
implementations").
Signed-off-by: NTommi Rantala <tt.rantala@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: davej@redhat.com
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/1365882554-30259-1-git-send-email-tt.rantala@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Changing uid/gid/projid mappings doesn't change your id within the
namespace; it reconfigures the namespace.  Unprivileged programs should
*not* be able to write these files.  (We're also checking the privileges
on the wrong task.)

Given the write-once nature of these files and the other security
checks, this is likely impossible to usefully exploit.
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>

Signed-off-by: NAndy Lutomirski <luto@amacapital.net>

When we require privilege for setting /proc/<pid>/uid_map or
/proc/<pid>/gid_map no longer allow an unprivileged user to
open the file and pass it to a privileged program to write
to the file.

Instead when privilege is required require both the opener and the
writer to have the necessary capabilities.

I have tested this code and verified that setting /proc/<pid>/uid_map
fails when an unprivileged user opens the file and a privielged user
attempts to set the mapping, that unprivileged users can still map
their own id, and that a privileged users can still setup an arbitrary
mapping.
Reported-by: NAndy Lutomirski <luto@amacapital.net>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndy Lutomirski <luto@amacapital.net>

Nothing is using it yet, but this will allow us to delay the open-time
checks to use time, without breaking the normal UNIX permission
semantics where permissions are determined by the opener (and the file
descriptor can then be passed to a different process, or the process can
drop capabilities).
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As ftrace_filter_lseek is now used with ftrace_pid_fops, it needs to
be moved out of the #ifdef CONFIG_DYNAMIC_FTRACE section as the
ftrace_pid_fops is defined when DYNAMIC_FTRACE is not.

Cc: stable@vger.kernel.org
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently set_ftrace_pid and set_graph_function files use seq_lseek
for their fops.  However seq_open() is called only for FMODE_READ in
the fops->open() so that if an user tries to seek one of those file
when she open it for writing, it sees NULL seq_file and then panic.

It can be easily reproduced with following command:

  $ cd /sys/kernel/debug/tracing
  $ echo 1234 | sudo tee -a set_ftrace_pid

In this example, GNU coreutils' tee opens the file with fopen(, "a")
and then the fopen() internally calls lseek().

Link: http://lkml.kernel.org/r/1365663302-2170-1-git-send-email-namhyung@kernel.org

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The smpboot threads rely on the park/unpark mechanism which binds per
cpu threads on a particular core. Though the functionality is racy:

CPU0	       	 	CPU1  	     	    CPU2
unpark(T)				    wake_up_process(T)
  clear(SHOULD_PARK)	T runs
			leave parkme() due to !SHOULD_PARK  
  bind_to(CPU2)		BUG_ON(wrong CPU)						    

We cannot let the tasks move themself to the target CPU as one of
those tasks is actually the migration thread itself, which requires
that it starts running on the target cpu right away.

The solution to this problem is to prevent wakeups in park mode which
are not from unpark(). That way we can guarantee that the association
of the task to the target cpu is working correctly.

Add a new task state (TASK_PARKED) which prevents other wakeups and
use this state explicitly for the unpark wakeup.

Peter noticed: Also, since the task state is visible to userspace and
all the parked tasks are still in the PID space, its a good hint in ps
and friends that these tasks aren't really there for the moment.

The migration thread has another related issue.

CPU0	      	     	 CPU1
Bring up CPU2
create_thread(T)
park(T)
 wait_for_completion()
			 parkme()
			 complete()
sched_set_stop_task()
			 schedule(TASK_PARKED)

The sched_set_stop_task() call is issued while the task is on the
runqueue of CPU1 and that confuses the hell out of the stop_task class
on that cpu. So we need the same synchronizaion before
sched_set_stop_task().
Reported-by: NDave Jones <davej@redhat.com>
Reported-and-tested-by: NDave Hansen <dave@sr71.net>
Reported-and-tested-by: NBorislav Petkov <bp@alien8.de>
Acked-by: NPeter Ziljstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: dhillf@gmail.com
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1304091635430.21884@ionosSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Fix to return -ENOMEM in the allocation error case instead of 0
(if pmu_bus_running == 1), as done elsewhere in this function.
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Cc: a.p.zijlstra@chello.nl
Cc: paulus@samba.org
Cc: acme@ghostprotocols.net
Link: http://lkml.kernel.org/r/CAPgLHd8j_fWcgqe%3DKLWjpBj%2B%3Do0Pw6Z-SEq%3DNTPU08c2w1tngQ@mail.gmail.com
[ Tweaked the error code setting placement and the changelog. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

sysfs started complaining about cases where permissions don't
match what's in the sysfs ops structure (such as allowing read
without a "show" callback).
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Cc: williams@redhat.com
Link: http://lkml.kernel.org/r/1363795105-5884-1-git-send-email-sasha.levin@oracle.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

On the failure path, stat->start and stat->pages will refer same page.
So it'll attempt to free the same page again and get kernel panic.

Link: http://lkml.kernel.org/r/1364820385-32027-1-git-send-email-namhyung@kernel.org

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>