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authorLai Jiangshan <laijs@cn.fujitsu.com>2009-04-02 16:58:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-02 19:05:00 -0700
commit2355b70fd59cb5be7de2052a9edeee7afb7ff099 (patch)
tree93f192f9dab4748a313ec8d78041b1937e232f33 /kernel
parent1ee1184485df9c9a3503d3a684b911fb7c73d259 (diff)
workqueue: avoid recursion in run_workqueue()
1) lockdep will complain when run_workqueue() performs recursion. 2) The recursive implementation of run_workqueue() means that flush_workqueue() and its documentation are inconsistent. This may hide deadlocks and other bugs. 3) The recursion in run_workqueue() will poison cwq->current_work, but flush_work() and __cancel_work_timer(), etcetera need a reliable cwq->current_work. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Eric Dumazet <dada1@cosmosbay.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/workqueue.c41
1 files changed, 11 insertions, 30 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9aedd9fd825..32f8e0d2bf5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -48,8 +48,6 @@ struct cpu_workqueue_struct {
struct workqueue_struct *wq;
struct task_struct *thread;
-
- int run_depth; /* Detect run_workqueue() recursion depth */
} ____cacheline_aligned;
/*
@@ -262,13 +260,6 @@ EXPORT_SYMBOL_GPL(queue_delayed_work_on);
static void run_workqueue(struct cpu_workqueue_struct *cwq)
{
spin_lock_irq(&cwq->lock);
- cwq->run_depth++;
- if (cwq->run_depth > 3) {
- /* morton gets to eat his hat */
- printk("%s: recursion depth exceeded: %d\n",
- __func__, cwq->run_depth);
- dump_stack();
- }
while (!list_empty(&cwq->worklist)) {
struct work_struct *work = list_entry(cwq->worklist.next,
struct work_struct, entry);
@@ -311,7 +302,6 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
spin_lock_irq(&cwq->lock);
cwq->current_work = NULL;
}
- cwq->run_depth--;
spin_unlock_irq(&cwq->lock);
}
@@ -368,29 +358,20 @@ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
{
- int active;
+ int active = 0;
+ struct wq_barrier barr;
- if (cwq->thread == current) {
- /*
- * Probably keventd trying to flush its own queue. So simply run
- * it by hand rather than deadlocking.
- */
- run_workqueue(cwq);
- active = 1;
- } else {
- struct wq_barrier barr;
+ WARN_ON(cwq->thread == current);
- active = 0;
- spin_lock_irq(&cwq->lock);
- if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
- insert_wq_barrier(cwq, &barr, &cwq->worklist);
- active = 1;
- }
- spin_unlock_irq(&cwq->lock);
-
- if (active)
- wait_for_completion(&barr.done);
+ spin_lock_irq(&cwq->lock);
+ if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
+ insert_wq_barrier(cwq, &barr, &cwq->worklist);
+ active = 1;
}
+ spin_unlock_irq(&cwq->lock);
+
+ if (active)
+ wait_for_completion(&barr.done);
return active;
}