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Message-ID: <1405325601-12437-2-git-send-email-laijs@cn.fujitsu.com> Date: Mon, 14 Jul 2014 16:13:21 +0800 From: Lai Jiangshan <laijs@...fujitsu.com> To: <linux-kernel@...r.kernel.org> CC: Tejun Heo <tj@...nel.org>, Lai Jiangshan <laijs@...fujitsu.com> Subject: [PATCH 1/1 V2] workqueue: remove the del_timer_sync()s in maybe_create_worker() 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 unless the manager is working it is a preparation/cleanup 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() the timer is still repeating, we should not use del_timer_sync(), let the timer dismiss itself. Change from V1: V1 incorrectly stops the timer when !need_to_create_worker(), but no one can restart it when needed. In V2, we stops the timer only when manager is not working. Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com> --- kernel/workqueue.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 338d418..9c86a64 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1864,10 +1864,11 @@ static void pool_mayday_timeout(unsigned long __pool) send_mayday(work); } + if (mutex_is_locked(&pool->manager_arb)) + 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); } /** @@ -1909,7 +1910,6 @@ 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))) @@ -1926,7 +1926,6 @@ restart: break; } - del_timer_sync(&pool->mayday_timer); spin_lock_irq(&pool->lock); if (need_to_create_worker(pool)) goto restart; -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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