Subject: Re: [PATCH 1/2] workqueue: Catch more locking problems with flush_work()

From: Stephen Boyd <[email-masked]>
Date: Fri, 20 Apr 2012 16:15:01 -0700

On 4/20/2012 10:35 AM, Tejun Heo wrote:
>
> All that's necessary is acquiring and releasing work->lockdep_map.
> There's no need to nest start_flush_work() inside it.  Without
> nesting, there's nothing to worry about ABBA lockdeps.

Yes I see. This patch should work then?

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5abf42f..038cf64 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2506,6 +2506,9 @@ bool flush_work(struct work_struct *work)
 {
        struct wq_barrier barr;

+       lock_map_acquire(&work->lockdep_map);
+       lock_map_release(&work->lockdep_map);
+
        if (start_flush_work(work, &barr, true)) {
                wait_for_completion(&barr.done);
                destroy_work_on_stack(&barr.work);

-- 
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