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authorTejun Heo <tj@kernel.org>2015-12-07 10:58:57 -0500
committerTejun Heo <tj@kernel.org>2015-12-08 11:29:36 -0500
commitfca839c00a12d682cb59b3b620d109a1d850b262 (patch)
tree5e7930d002412222645eca18e77343969262f75c /kernel/workqueue.c
parent527e9316f8ec44bd53d90fb9f611fa7ffff52bb9 (diff)
downloadlinux-sh-fca839c00a12d682cb59b3b620d109a1d850b262.tar.gz
workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue
Task or work item involved in memory reclaim trying to flush a non-WQ_MEM_RECLAIM workqueue or one of its work items can lead to deadlock. Trigger WARN_ONCE() if such conditions are detected. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c579dbab2e36..c7769c507bf5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2316,6 +2316,37 @@ repeat:
goto repeat;
}
+/**
+ * check_flush_dependency - check for flush dependency sanity
+ * @target_wq: workqueue being flushed
+ * @target_work: work item being flushed (NULL for workqueue flushes)
+ *
+ * %current is trying to flush the whole @target_wq or @target_work on it.
+ * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
+ * reclaiming memory or running on a workqueue which doesn't have
+ * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
+ * a deadlock.
+ */
+static void check_flush_dependency(struct workqueue_struct *target_wq,
+ struct work_struct *target_work)
+{
+ work_func_t target_func = target_work ? target_work->func : NULL;
+ struct worker *worker;
+
+ if (target_wq->flags & WQ_MEM_RECLAIM)
+ return;
+
+ worker = current_wq_worker();
+
+ WARN_ONCE(current->flags & PF_MEMALLOC,
+ "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
+ current->pid, current->comm, target_wq->name, target_func);
+ WARN_ONCE(worker && (worker->current_pwq->wq->flags & WQ_MEM_RECLAIM),
+ "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
+ worker->current_pwq->wq->name, worker->current_func,
+ target_wq->name, target_func);
+}
+
struct wq_barrier {
struct work_struct work;
struct completion done;
@@ -2525,6 +2556,8 @@ void flush_workqueue(struct workqueue_struct *wq)
list_add_tail(&this_flusher.list, &wq->flusher_overflow);
}
+ check_flush_dependency(wq, NULL);
+
mutex_unlock(&wq->mutex);
wait_for_completion(&this_flusher.done);
@@ -2697,6 +2730,8 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
pwq = worker->current_pwq;
}
+ check_flush_dependency(pwq->wq, work);
+
insert_wq_barrier(pwq, barr, work, worker);
spin_unlock_irq(&pool->lock);