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authorJohannes Berg <johannes.berg@intel.com>2018-08-22 11:49:03 +0200
committerTejun Heo <tj@kernel.org>2018-08-22 08:31:37 -0700
commitd6e89786bed977f37f55ffca11e563f6d2b1e3b5 (patch)
tree099c38c86ac779dfe984e119370032dc16443247
parent66448bc274cadedb71fda7d914e7c29d8dead217 (diff)
workqueue: skip lockdep wq dependency in cancel_work_sync()
In cancel_work_sync(), we can only have one of two cases, even with an ordered workqueue: * the work isn't running, just cancelled before it started * the work is running, but then nothing else can be on the workqueue before it Thus, we need to skip the lockdep workqueue dependency handling, otherwise we get false positive reports from lockdep saying that we have a potential deadlock when the workqueue also has other work items with locking, e.g. work1_function() { mutex_lock(&mutex); ... } work2_function() { /* nothing */ } other_function() { queue_work(ordered_wq, &work1); queue_work(ordered_wq, &work2); mutex_lock(&mutex); cancel_work_sync(&work2); } As described above, this isn't a problem, but lockdep will currently flag it as if cancel_work_sync() was flush_work(), which *is* a problem. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/workqueue.c37
1 files changed, 22 insertions, 15 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7ea75529eabb..aa520e715bbc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2843,7 +2843,8 @@ reflush:
}
EXPORT_SYMBOL_GPL(drain_workqueue);
-static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
+static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
+ bool from_cancel)
{
struct worker *worker = NULL;
struct worker_pool *pool;
@@ -2885,7 +2886,8 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
* workqueues the deadlock happens when the rescuer stalls, blocking
* forward progress.
*/
- if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) {
+ if (!from_cancel &&
+ (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
lock_map_acquire(&pwq->wq->lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);
}
@@ -2896,6 +2898,22 @@ already_gone:
return false;
}
+static bool __flush_work(struct work_struct *work, bool from_cancel)
+{
+ struct wq_barrier barr;
+
+ if (WARN_ON(!wq_online))
+ return false;
+
+ if (start_flush_work(work, &barr, from_cancel)) {
+ wait_for_completion(&barr.done);
+ destroy_work_on_stack(&barr.work);
+ return true;
+ } else {
+ return false;
+ }
+}
+
/**
* flush_work - wait for a work to finish executing the last queueing instance
* @work: the work to flush
@@ -2909,18 +2927,7 @@ already_gone:
*/
bool flush_work(struct work_struct *work)
{
- struct wq_barrier barr;
-
- if (WARN_ON(!wq_online))
- return false;
-
- if (start_flush_work(work, &barr)) {
- wait_for_completion(&barr.done);
- destroy_work_on_stack(&barr.work);
- return true;
- } else {
- return false;
- }
+ return __flush_work(work, false);
}
EXPORT_SYMBOL_GPL(flush_work);
@@ -2986,7 +2993,7 @@ static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
* isn't executing.
*/
if (wq_online)
- flush_work(work);
+ __flush_work(work, true);
clear_work_data(work);