sched: Do not attempt to destroy uninitialized rt_bandwidth
authorBianca Lutz <sowilo@cs.tu-berlin.de>
Wed, 13 Jul 2011 18:13:36 +0000 (20:13 +0200)
committerIngo Molnar <mingo@elte.hu>
Thu, 21 Jul 2011 16:01:51 +0000 (18:01 +0200)
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>
kernel/sched.c

index 3b3826e..f107204 100644 (file)
@@ -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)