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author | Stephen Boyd <sboyd@codeaurora.org> | 2012-04-20 17:28:50 -0700 |
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committer | Tejun Heo <tj@kernel.org> | 2012-04-23 11:06:42 -0700 |
commit | 0976dfc1d0cd80a4e9dfaf87bd8744612bde475a (patch) | |
tree | 0af2d79070fcb0a510187eb780db796c5702df20 /kernel/workqueue.c | |
parent | f5b2552b4ebbeadcadde1532d7bbd3f850719046 (diff) | |
download | linux-0976dfc1d0cd80a4e9dfaf87bd8744612bde475a.tar.gz |
workqueue: Catch more locking problems with flush_work()
If a workqueue is flushed with flush_work() lockdep checking can 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 not always print a warning when flush_work() was called. In this trivial example nothing could go wrong since we are guaranteed module_init() and module_exit() don't run concurrently, but if the work item is schedule asynchronously we could have a scenario where the work item is running just at the time flush_work() is called resulting in a classic ABBA locking problem. Add a lockdep hint by acquiring and releasing the work item lockdep_map in flush_work() so that we always catch this potential deadlock scenario. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Yong Zhang <yong.zhang0@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r-- | kernel/workqueue.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 66ec08de6dac..211eadb23323 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2509,6 +2509,9 @@ 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); |