try_to_grab_pending() leave LINKED tagalong in delayed queue when
it deletes a work. This behavior will cause future
cwq_activate_first_delayed() increase the ->nr_active wrongly,
and may cause the whole cwq frozen.
example:
state: cwq->max_active = 1, cwq->nr_active = 1
one work in cwq->pool, many in cwq->delayed_works.
step1: try_to_grab_pending() remove a work from delayed_works but leave
tagalong.
step2: when the work in cwq->pool is finished, cwq_activate_first_delayed()
move the tagalong to cwq->pool and increase the ->nr_active.
current state: cwq->nr_active = 1, but works of the cwq in cwq->pool are all
NO_COLOR,
so even when these works are finished, cwq->nr_active will not be
decreased,
and no work will be moved from cwq->delayed_works. the cwq is frozen.
Fix it by moving the tagalong to cwq->pool in try_to_grab_pending().
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7b91332..1a268b2 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1101,11 +1101,26 @@ static int try_to_grab_pending(struct work_struct
*work, bool is_dwork,
*/
smp_rmb();
if (gcwq == get_work_gcwq(work)) {
+ unsigned long delayed;
+
+ /*
+ * move LINKED tagalong(if exist) out from
+ * delayed queue. Otherwise some future
+ * cwq_activate_first_delayed() may move
+ * works(which are all NO_COLOR) to cwq->pool
+ * and increase the ->nr_active. It may
+ * cause the whole cwq frozen.
+ */
+ delayed = *work_data_bits(work) & WORK_STRUCT_DELAYED;
+ if (delayed)
+ move_linked_works(work,
+ &get_work_cwq(work)->pool->worklist,
+ NULL);
+
debug_work_deactivate(work);
list_del_init(&work->entry);
cwq_dec_nr_in_flight(get_work_cwq(work),
- get_work_color(work),
- *work_data_bits(work) & WORK_STRUCT_DELAYED);
+ get_work_color(work), delayed);
spin_unlock(&gcwq->lock);
return 1;
--
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