It is said in the document that the timer which is being
deleted by del_timer_sync() should not be restarted:
Synchronization rules: Callers must prevent restarting of
the timer, otherwise this function is meaningless.
Repeating timer may cause the del_timer_sync() spin longer,
or even spin forever in very very very very extreme condition.
It is not considered a bug for me, but it disobeys the document.
To fix it, we need:
1) don't requeue the mayday timer when !need_to_create_worker()
it is a preparation/cleaup step for the fix. Otherwise the timer
will repeat forever if we only do the 2).
2) remove the del_timer_sync()s in maybe_create_worker()
Fix the problem. It is not enough if we only do the 1),
need_to_create_worker() would be probably true when the time
del_timer_sync() is called, the timer is still repeating.
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/workqueue.c | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 35974ac..593b9bc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1866,12 +1866,12 @@ static void pool_mayday_timeout(unsigned long __pool)
*/
list_for_each_entry(work, &pool->worklist, entry)
send_mayday(work);
+
+ mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
}
spin_unlock(&pool->lock);
spin_unlock_irq(&wq_mayday_lock);
-
- mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
}
/**
@@ -1913,7 +1913,6 @@ restart:
worker = create_worker(pool);
if (worker) {
- del_timer_sync(&pool->mayday_timer);
spin_lock_irq(&pool->lock);
start_worker(worker);
if (WARN_ON_ONCE(need_to_create_worker(pool)))
@@ -1931,7 +1930,6 @@ restart:
break;
}
- del_timer_sync(&pool->mayday_timer);
spin_lock_irq(&pool->lock);
if (need_to_create_worker(pool))
goto restart;
--
1.7.7.6
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