We assign cpu id into work struct's data field in __queue_delayed_work_on().
In current implementation, when work is come in first time,
current running cpu id is assigned.
If we do __queue_delayed_work_on() with CPU A on CPU B,
__queue_work() invoked in delayed_work_timer_fn() go into
the following sub-optimal path in case of WQ_NON_REENTRANT.
gcwq = get_gcwq(cpu);
if (wq->flags & WQ_NON_REENTRANT &&
(last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
Change lcpu to @cpu and rechange lcpu to local cpu if lcpu is WORK_CPU_UNBOUND.
It is sufficient to prevent to go into sub-optimal path.
Signed-off-by: Joonsoo Kim <js1...@gmail.com>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c29f2dc..32c4f79 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1356,9 +1356,16 @@ static void __queue_delayed_work(int cpu, struct
workqueue_struct *wq,
if (!(wq->flags & WQ_UNBOUND)) {
struct global_cwq *gcwq = get_work_gcwq(work);
- if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
+ /*
+ * If we cannot get gcwq from work directly, we should
+ * deliberately select last cpu not to go into sub-optimal
+ * path of reentrance detection for delayed work. In this case,
+ * we assign requested cpu to lcpu except WORK_CPU_UNBOUND
+ */
+ lcpu = cpu;
+ if (gcwq)
lcpu = gcwq->cpu;
- else
+ if (lcpu == WORK_CPU_UNBOUND)
lcpu = raw_smp_processor_id();
} else {
lcpu = WORK_CPU_UNBOUND;
--
1.7.9.5
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