From 99bc52429f11d1f4f81495ac8237085aaeb6bccf Mon Sep 17 00:00:00 2001
From: Bianca Lutz <sowilo@cs.tu-berlin.de>
Date: Wed, 13 Jul 2011 20:13:36 +0200
Subject: [PATCH] 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>
---
kernel/sched.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 3b3826ebe793..f107204db53f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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)
--
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