linux-stable.git/kernel/sched/auto_group.c, branch linux-4.8.y

sched/autogroup: Fix 64-bit kernel nice level adjustment

2016-12-15T16:50:35+00:00

commit 83929cce95251cc77e5659bf493bd424ae0e7a67 upstream.

Michael Kerrisk reported:

> Regarding the previous paragraph...  My tests indicate
> that writing *any* value to the autogroup [nice priority level]
> file causes the task group to get a lower priority.

Because autogroup didn't call the then meaningless scale_load()...

Autogroup nice level adjustment has been broken ever since load
resolution was increased for 64-bit kernels.  Use scale_load() to
scale group weight.

Michael Kerrisk tested this patch to fix the problem:

> Applied and tested against 4.9-rc6 on an Intel u7 (4 cores).
> Test setup:
>
> Terminal window 1: running 40 CPU burner jobs
> Terminal window 2: running 40 CPU burner jobs
> Terminal window 1: running  1 CPU burner job
>
> Demonstrated that:
> * Writing "0" to the autogroup file for TW1 now causes no change
>   to the rate at which the process on the terminal consume CPU.
> * Writing -20 to the autogroup file for TW1 caused those processes
>   to get the lion's share of CPU while TW2 TW3 get a tiny amount.
> * Writing -20 to the autogroup files for TW1 and TW3 allowed the
>   process on TW3 to get as much CPU as it was getting as when
>   the autogroup nice values for both terminals were 0.

Reported-by: Michael Kerrisk 
Tested-by: Michael Kerrisk 
Signed-off-by: Mike Galbraith 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-man 
Link: http://lkml.kernel.org/r/1479897217.4306.6.camel@gmx.de
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched/core: Move the sched_to_prio[] arrays out of line

2015-12-04T09:34:46+00:00

When building a kernel with a gcc 6 snapshot the compiler complains
about unused const static variables for prio_to_weight and prio_to_mult
for multiple scheduler files (all but core.c and autogroup.c)

The way the array is currently declared it will be duplicated in
every scheduler file that includes sched.h, which seems rather wasteful.

Move the array out of line into core.c. I also added a sched_ prefix
to avoid any potential name space collisions.

Signed-off-by: Andi Kleen 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1448859583-3252-1-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar

sched, timer: Convert usages of ACCESS_ONCE() in the scheduler to READ_ONCE()/WRITE_ONCE()

2015-05-08T10:11:32+00:00

ACCESS_ONCE doesn't work reliably on non-scalar types. This patch removes
the rest of the existing usages of ACCESS_ONCE() in the scheduler, and use
the new READ_ONCE() and WRITE_ONCE() APIs as appropriate.

Signed-off-by: Jason Low 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Thomas Gleixner 
Acked-by: Rik van Riel 
Acked-by: Waiman Long 
Cc: Andrew Morton 
Cc: Aswin Chandramouleeswaran 
Cc: Borislav Petkov 
Cc: Davidlohr Bueso 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Mike Galbraith 
Cc: Oleg Nesterov 
Cc: Paul E. McKenney 
Cc: Preeti U Murthy 
Cc: Scott J Norton 
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/1430251224-5764-2-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar

sched/autogroup: Remove unnecessary #ifdef guards

2015-04-16T07:20:43+00:00

Since commit:

  029632fbb7b7 ("sched: Make separate sched*.c translation units")

autogroup is a separate translation unit built from the Makefile and
thus no longer needs its content wrapped with #ifdef CONFIG_SCHED_AUTOGROUP.

Signed-off-by: Tobias Klauser 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1429116678-17000-1-git-send-email-tklauser@distanz.ch
Signed-off-by: Ingo Molnar

sched/autogroup: Fix failure to set cpu.rt_runtime_us

2015-02-18T15:17:20+00:00

Because task_group() uses a cache of autogroup_task_group(), whose
output depends on sched_class, switching classes can generate
problems.

In particular, when started as fair, the cache points to the
autogroup, so when switching to RT the tg_rt_schedulable() test fails
for every cpu.rt_{runtime,period}_us change because now the autogroup
has tasks and no runtime.

Furthermore, going back to the previous semantics of varying
task_group() with sched_class has the down-side that the sched_debug
output varies as well, even though the task really is in the
autogroup.

Therefore add an autogroup exception to tg_has_rt_tasks() -- such that
both (all) task_group() usages in sched/core now have one. And remove
all the remnants of the variable task_group() output.

Reported-by: Zefan Li 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Stefan Bader 
Fixes: 8323f26ce342 ("sched: Fix race in task_group()")
Link: http://lkml.kernel.org/r/20150209112237.GR5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

sched: Change autogroup_move_group() to use for_each_thread()

2014-08-20T07:47:18+00:00

Change autogroup_move_group() to use for_each_thread() instead of
buggy while_each_thread().

Signed-off-by: Oleg Nesterov 
Signed-off-by: Peter Zijlstra 
Cc: Mike Galbraith 
Cc: Hidetoshi Seto 
Cc: Frank Mayhar 
Cc: Frederic Weisbecker 
Cc: Andrew Morton 
Cc: Sanjay Rao 
Cc: Larry Woodman 
Cc: Rik van Riel 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/20140813192003.GA19334@redhat.com
Signed-off-by: Ingo Molnar

sched: Replace hardcoding of -20 and 19 with MIN_NICE and MAX_NICE

2014-02-22T17:15:54+00:00

Signed-off-by: Dongsheng Yang 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/bd80780f19b4f9b4a765acc353c8dbc130274dd6.1392103744.git.yangds.fnst@cn.fujitsu.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Ingo Molnar

sched/autogroup: Fix race with task_groups list

2013-05-28T07:40:22+00:00

In autogroup_create(), a tg is allocated and added to the task_groups
list. If CONFIG_RT_GROUP_SCHED is set, this tg is then modified while on
the list, without locking. This can race with someone walking the list,
like __enable_runtime() during CPU unplug, and result in a use-after-free
bug.

To fix this, move sched_online_group(), which adds the tg to the list,
to the end of the autogroup_create() function after the modification.

Signed-off-by: Gerald Schaefer 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1369411669-46971-2-git-send-email-gerald.schaefer@de.ibm.com
Signed-off-by: Ingo Molnar

sched: split out css_online/css_offline from tg creation/destruction

2013-01-24T20:05:18+00:00

This is a preparaton for later patches.

- What do we gain from cpu_cgroup_css_online():

After ss->css_alloc() and before ss->css_online(), there's a small
window that tg->css.cgroup is NULL. With this change, tg won't be seen
before ss->css_online(), where it's added to the global list, so we're
guaranteed we'll never see NULL tg->css.cgroup.

- What do we gain from cpu_cgroup_css_offline():

tg is freed via RCU, so is cgroup. Without this change, This is how
synchronization works:

cgroup_rmdir()
  no ss->css_offline()
diput()
  syncornize_rcu()
  ss->css_free()       <-- unregister tg, and free it via call_rcu()
  kfree_rcu(cgroup)    <-- wait possible refs to cgroup, and free cgroup

We can't just kfree(cgroup), because tg might access tg->css.cgroup.

With this change:

cgroup_rmdir()
  ss->css_offline()    <-- unregister tg
diput()
  synchronize_rcu()    <-- wait possible refs to tg and cgroup
  ss->css_free()       <-- free tg
  kfree_rcu(cgroup)    <-- free cgroup

As you see, kfree_rcu() is redundant now.

Signed-off-by: Li Zefan 
Signed-off-by: Tejun Heo 
Acked-by: Ingo Molnar

Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"

2012-12-11T09:23:45+00:00

This reverts commit 5258f386ea4e8454bc801fb443e8a4217da1947c,
because the underlying autogroups bug got fixed upstream in
a better way, via:

  fd8ef11730f1 Revert "sched, autogroup: Stop going ahead if autogroup is disabled"

Cc: Mike Galbraith 
Cc: Yong Zhang 
Cc: Peter Zijlstra 
Cc: Linus Torvalds 
Signed-off-by: Ingo Molnar