When pwq->refcnt == 0, the retrying is guaranteed to make forward-progress.
The comment above the code explains it well:
/*
* pwq is determined and locked. For unbound pools, we could have
* raced with pwq release and it could already be dead. If its
* refcnt is zero, repeat pwq selection. Note that pwqs never die
* without another pwq replacing it in the numa_pwq_tbl or while
* work items are executing on it, so the retrying is guaranteed to
* make forward-progress.
*/
It means the cpu_relax() here is useless and sometimes misleading,
it should retry directly and make some progress rather than waste time.
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/workqueue.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 23f9a2b..98b38b5 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1368,7 +1368,6 @@ retry:
if (unlikely(!pwq->refcnt)) {
if (wq->flags & WQ_UNBOUND) {
spin_unlock(&pwq->pool->lock);
- cpu_relax();
goto retry;
}
/* oops */
--
1.7.4.4
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