diff options
| author | Tejun Heo <tj@kernel.org> | 2011-04-29 18:08:37 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-05-09 15:06:37 -0700 |
| commit | 5a19c7ecdc631407d490d206b80ed790daad99cd (patch) | |
| tree | c1cb59e08e914df903ca5f70ba6264033b62c5b6 /kernel | |
| parent | bcd0df39767d1c4352566d909291deac099b222b (diff) | |
workqueue: fix deadlock in worker_maybe_bind_and_lock()
commit 5035b20fa5cd146b66f5f89619c20a4177fb736d upstream.
If a rescuer and stop_machine() bringing down a CPU race with each
other, they may deadlock on non-preemptive kernel. The CPU won't
accept a new task, so the rescuer can't migrate to the target CPU,
while stop_machine() can't proceed because the rescuer is holding one
of the CPU retrying migration. GCWQ_DISASSOCIATED is never cleared
and worker_maybe_bind_and_lock() retries indefinitely.
This problem can be reproduced semi reliably while the system is
entering suspend.
http://thread.gmane.org/gmane.linux.kernel/1122051
A lot of kudos to Thilo-Alexander for reporting this tricky issue and
painstaking testing.
stable: This affects all kernels with cmwq, so all kernels since and
including v2.6.36 need this fix.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Thilo-Alexander Ginkel <thilo@ginkel.com>
Tested-by: Thilo-Alexander Ginkel <thilo@ginkel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index ee6578b578a..7b65ae747c6 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1283,8 +1283,14 @@ __acquires(&gcwq->lock) return true; spin_unlock_irq(&gcwq->lock); - /* CPU has come up inbetween, retry migration */ + /* + * We've raced with CPU hot[un]plug. Give it a breather + * and retry migration. cond_resched() is required here; + * otherwise, we might deadlock against cpu_stop trying to + * bring down the CPU on non-preemptive kernel. + */ cpu_relax(); + cond_resched(); } } |