linux-toradex.git/kernel/sched/auto_group.c, branch v4.4.84

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

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

2012-10-30T09:26:04+00:00

Due to these two commits:

  8323f26ce342 sched: Fix race in task_group()
  800d4d30c8f2 sched, autogroup: Stop going ahead if autogroup is disabled

... autogroup scheduling's dynamic knobs are wrecked.

With both patches applied, all you have to do to crash a box is
disable autogroup during boot up, then reboot.. boom, NULL pointer
dereference due to 800d4d30 not allowing autogroup to move things,
and 8323f26ce making that the only way to switch runqueues.

Remove most of the (dysfunctional) knobs and turn the remaining
sched_autogroup_enabled knob readonly.

If the user fiddles with cgroups hereafter, once tasks
are moved, autogroup won't mess with them again unless
they call setsid().

No knobs, no glitz, nada, just a cute little thing folks can
turn on if they don't want to muck about with cgroups and/or
systemd.

Signed-off-by: Mike Galbraith 
Cc: Xiaotian Feng 
Cc: Peter Zijlstra 
Cc: Xiaotian Feng 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Oleg Nesterov 
Cc:  # v3.6
Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.net
Signed-off-by: Ingo Molnar

sched: Clean up parameter passing of proc_sched_autogroup_set_nice()

2012-03-02T11:23:49+00:00

Pass nice as a value to proc_sched_autogroup_set_nice().

No side effect is expected, and the variable err will be overwritten with
the return value.

Signed-off-by: Hiroshi Shimamoto 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/4F45FBB7.5090607@ct.jp.nec.com
Signed-off-by: Ingo Molnar