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sched: Do not attempt to destroy uninitialized rt_bandwidth 

If a task group is to be created and alloc_fair_sched_group() fails,
then the rt_bandwidth of the corresponding task group is not yet
initialized. The caller, sched_create_group(), starts a clean up
procedure which calls free_rt_sched_group() which unconditionally
destroys the not yet initialized rt_bandwidth.

This crashes or hangs the system in lock_hrtimer_base(): UP systems
dereference a NULL pointer, while SMP systems loop endlessly on a
condition that cannot become true.

This patch simply avoids the destruction of rt_bandwidth when the
initialization code path was not reached.

(This was discovered by accident with a custom kernel modification.)

Signed-off-by: Bianca Lutz <sowilo@cs.tu-berlin.de>
Signed-off-by: Jan Schoenherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1310580816-10861-7-git-send-email-schnhrr@cs.tu-berlin.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Bianca Lutz 2011-07-13 20:13:36 +02:00 committed by Ingo Molnar
parent 045176d22f
commit 99bc52429f
1 changed files with 2 additions and 1 deletions
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3
kernel/sched.c
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@ -8383,7 +8383,8 @@ static void free_rt_sched_group(struct task_group *tg)
{
int i;
destroy_rt_bandwidth(&tg->rt_bandwidth);
if (tg->rt_se)
destroy_rt_bandwidth(&tg->rt_bandwidth);
for_each_possible_cpu(i) {
if (tg->rt_rq)