sched/fair: Reset se-depth when task switched to FAIR
authorMichael wang <wangyun@linux.vnet.ibm.com>
Thu, 20 Feb 2014 03:14:53 +0000 (11:14 +0800)
committerThomas Gleixner <tglx@linutronix.de>
Fri, 21 Feb 2014 20:43:17 +0000 (21:43 +0100)
commiteb7a59b2c888c2518ba2c9d0020343ca71aa9dee
treef9957db29515004d0dae2af3f48af6607f88af73
parentd97a860c4f3de98ba5040a22f305b7159fe17cff
sched/fair: Reset se-depth when task switched to FAIR

Sasha reported:

[  522.645288] BUG: unable to handle kernel NULL pointer dereference at ...
[  522.646271] IP: [<ffffffff81186c6f>] check_preempt_wakeup+0x11f/0x210
...
[  522.650021] Call Trace:
[  522.650021]  <IRQ>
[  522.650021]  [<ffffffff8117361d>] check_preempt_curr+0x3d/0xb0
[  522.650021]  [<ffffffff81175d88>] ttwu_do_wakeup+0x18/0x130
...

which was caused by the se-depth changed during the time when task is not
FAIR, and we will use the wrong depth value after it switched back to FAIR.

This patch reset the depth at the time when task switched to FAIR, make sure
that we always have the correct value when task is FAIR.

Cc: Ingo Molnar <mingo@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5305732D.70001@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
kernel/sched/fair.c