From: Stephen Boyd <sboyd@codeaurora.org>
To: linux-kernel@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>,
netdev@vger.kernel.org, Ben Dooks <ben-linux@fluff.org>
Subject: [PATCH 1/2] workqueue: Catch more locking problems with flush_work()
Date: Wed, 18 Apr 2012 20:25:57 -0700 [thread overview]
Message-ID: <1334805958-29119-1-git-send-email-sboyd@codeaurora.org> (raw)
If a workqueue is flushed but the work item is not scheduled to
run, lockdep checking will be circumvented. For example:
static DEFINE_MUTEX(mutex);
static void my_work(struct work_struct *w)
{
mutex_lock(&mutex);
mutex_unlock(&mutex);
}
static DECLARE_WORK(work, my_work);
static int __init start_test_module(void)
{
schedule_work(&work);
return 0;
}
module_init(start_test_module);
static void __exit stop_test_module(void)
{
mutex_lock(&mutex);
flush_work(&work);
mutex_unlock(&mutex);
}
module_exit(stop_test_module);
would only print a warning if the work item was actively running
when flush_work() was called. Otherwise flush_work() returns
early. In this trivial example nothing could go wrong, but if the
work item is schedule via an interrupt we could potentially have a
scenario where the work item is running just at the time flush_work()
is called. This could become a classic AB-BA locking problem.
Add a lockdep hint in flush_work() in the "work not running" case
so that we always catch this potential deadlock scenario.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
kernel/workqueue.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 66ec08d..eb800df 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2513,8 +2513,11 @@ bool flush_work(struct work_struct *work)
wait_for_completion(&barr.done);
destroy_work_on_stack(&barr.work);
return true;
- } else
+ } else {
+ lock_map_acquire(&work->lockdep_map);
+ lock_map_release(&work->lockdep_map);
return false;
+ }
}
EXPORT_SYMBOL_GPL(flush_work);
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
next reply other threads:[~2012-04-19 3:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-19 3:25 Stephen Boyd [this message]
2012-04-19 3:25 ` [PATCH 2/2] ks8851: Fix mutex deadlock in ks8851_net_stop() Stephen Boyd
2012-04-21 19:34 ` David Miller
2012-04-19 8:10 ` [PATCH 1/2] workqueue: Catch more locking problems with flush_work() Yong Zhang
2012-04-19 18:36 ` Stephen Boyd
2012-04-20 5:26 ` Yong Zhang
2012-04-20 6:01 ` Yong Zhang
2012-04-20 6:26 ` Stephen Boyd
2012-04-20 7:18 ` Yong Zhang
2012-04-20 8:18 ` Stephen Boyd
2012-04-20 8:32 ` Yong Zhang
2012-04-21 0:32 ` Yong Zhang
2012-04-19 15:28 ` Tejun Heo
2012-04-19 18:10 ` Stephen Boyd
2012-04-20 17:35 ` Tejun Heo
2012-04-20 23:15 ` Stephen Boyd
2012-04-21 0:28 ` [PATCHv2] " Stephen Boyd
2012-04-21 0:34 ` Yong Zhang
2012-04-23 18:07 ` Tejun Heo
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