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Subject[tip:sched/urgent] sched/fair: Fix RCU stall upon -ENOMEM in sched_create_group()
Commit-ID:  7f1a169b88f513e32a432ca0f85bfd282d117bd6
Gitweb: http://git.kernel.org/tip/7f1a169b88f513e32a432ca0f85bfd282d117bd6
Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
AuthorDate: Thu, 25 Dec 2014 15:51:21 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 9 Jan 2015 11:19:00 +0100

sched/fair: Fix RCU stall upon -ENOMEM in sched_create_group()

When alloc_fair_sched_group() in sched_create_group() fails,
free_sched_group() is called, and free_fair_sched_group() is called by
free_sched_group(). Since destroy_cfs_bandwidth() is called by
free_fair_sched_group() without calling init_cfs_bandwidth(),
RCU stall occurs at hrtimer_cancel():

INFO: rcu_sched self-detected stall on CPU { 1} (t=60000 jiffies g=13074 c=13073 q=0)
Task dump for CPU 1:
(fprintd) R running task 0 6249 1 0x00000088
...
Call Trace:
<IRQ> [<ffffffff81094988>] sched_show_task+0xa8/0x110
[<ffffffff81097acd>] dump_cpu_task+0x3d/0x50
[<ffffffff810c3a80>] rcu_dump_cpu_stacks+0x90/0xd0
[<ffffffff810c7751>] rcu_check_callbacks+0x491/0x700
[<ffffffff810cbf2b>] update_process_times+0x4b/0x80
[<ffffffff810db046>] tick_sched_handle.isra.20+0x36/0x50
[<ffffffff810db0a2>] tick_sched_timer+0x42/0x70
[<ffffffff810ccb19>] __run_hrtimer+0x69/0x1a0
[<ffffffff810db060>] ? tick_sched_handle.isra.20+0x50/0x50
[<ffffffff810ccedf>] hrtimer_interrupt+0xef/0x230
[<ffffffff810452cb>] local_apic_timer_interrupt+0x3b/0x70
[<ffffffff8164a465>] smp_apic_timer_interrupt+0x45/0x60
[<ffffffff816485bd>] apic_timer_interrupt+0x6d/0x80
<EOI> [<ffffffff810cc588>] ? lock_hrtimer_base.isra.23+0x18/0x50
[<ffffffff81193cf1>] ? __kmalloc+0x211/0x230
[<ffffffff810cc9d2>] hrtimer_try_to_cancel+0x22/0xd0
[<ffffffff81193cf1>] ? __kmalloc+0x211/0x230
[<ffffffff810ccaa2>] hrtimer_cancel+0x22/0x30
[<ffffffff810a3cb5>] free_fair_sched_group+0x25/0xd0
[<ffffffff8108df46>] free_sched_group+0x16/0x40
[<ffffffff810971bb>] sched_create_group+0x4b/0x80
[<ffffffff810aa383>] sched_autogroup_create_attach+0x43/0x1c0
[<ffffffff8107dc9c>] sys_setsid+0x7c/0x110
[<ffffffff81647729>] system_call_fastpath+0x12/0x17

Check whether init_cfs_bandwidth() was called before calling
destroy_cfs_bandwidth().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
[ Move the check into destroy_cfs_bandwidth() to aid compilability. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/201412252210.GCC30204.SOMVFFOtQJFLOH@I-love.SAKURA.ne.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6b99659..40667cb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4005,6 +4005,10 @@ void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force)

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
+ /* init_cfs_bandwidth() was not called */
+ if (!cfs_b->throttled_cfs_rq.next)
+ return;
+
hrtimer_cancel(&cfs_b->period_timer);
hrtimer_cancel(&cfs_b->slack_timer);
}

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