xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

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

Browse Source 
Due to these two commits:

  8323f26ce3 sched: Fix race in task_group()
  800d4d30c8 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 <efault@gmx.de>
Cc: Xiaotian Feng <xtfeng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xiaotian Feng <dannyfeng@tencent.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org> # v3.6
Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mike Galbraith
2012-10-28 12:19:23 -07:00
committed by Ingo Molnar
parent 8ed92e51f9
commit 5258f386ea
4 changed files with 14 additions and 147 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
kernel/sched/auto_group.h
View File

@@ -4,11 +4,6 @@
#include <linux/rwsem.h>
struct autogroup {
/*
* reference doesn't mean how many thread attach to this
* autogroup now. It just stands for the number of task
* could use this autogroup.
*/
struct kref kref;
struct task_group *tg;
struct rw_semaphore lock;
@@ -29,9 +24,7 @@ extern bool task_wants_autogroup(struct task_struct *p, struct task_group *tg);
static inline struct task_group *
autogroup_task_group(struct task_struct *p, struct task_group *tg)
{
int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
if (enabled && task_wants_autogroup(p, tg))
if (task_wants_autogroup(p, tg))
return p->signal->autogroup->tg;
return tg;