From 1265057fa02c7bed3b6d9ddc8a2048065a370364 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 8 Aug 2012 09:38:42 -0700 Subject: [PATCH] workqueue: fix CPU binding of flush_delayed_work[_sync]() delayed_work encodes the workqueue to use and the last CPU in delayed_work->work.data while it's on timer. The target CPU is implicitly recorded as the CPU the timer is queued on and delayed_work_timer_fn() queues delayed_work->work to the CPU it is running on. Unfortunately, this leaves flush_delayed_work[_sync]() no way to find out which CPU the delayed_work was queued for when they try to re-queue after killing the timer. Currently, it chooses the local CPU flush is running on. This can unexpectedly move a delayed_work queued on a specific CPU to another CPU and lead to subtle errors. There isn't much point in trying to save several bytes in struct delayed_work, which is already close to a hundred bytes on 64bit with all debug options turned off. This patch adds delayed_work->cpu to remember the CPU it's queued for. Note that if the timer is migrated during CPU down, the work item could be queued to the downed global_cwq after this change. As a detached global_cwq behaves like an unbound one, this doesn't change much for the delayed_work. Signed-off-by: Tejun Heo Cc: Linus Torvalds Cc: Ingo Molnar Cc: Andrew Morton --- include/linux/workqueue.h | 1 + kernel/workqueue.c | 7 ++++--- 2 files changed, 5 insertions(+), 3 deletions(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 20000305a8a6..b14d5d59af7c 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -102,6 +102,7 @@ struct work_struct { struct delayed_work { struct work_struct work; struct timer_list timer; + int cpu; }; static inline struct delayed_work *to_delayed_work(struct work_struct *work) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 41ae2c0979fe..11723c5b2b20 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1319,7 +1319,7 @@ void delayed_work_timer_fn(unsigned long __data) struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work); local_irq_disable(); - __queue_work(WORK_CPU_UNBOUND, cwq->wq, &dwork->work); + __queue_work(dwork->cpu, cwq->wq, &dwork->work); local_irq_enable(); } EXPORT_SYMBOL_GPL(delayed_work_timer_fn); @@ -1356,6 +1356,7 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, set_work_cwq(work, get_cwq(lcpu, wq), 0); + dwork->cpu = cpu; timer->expires = jiffies + delay; if (unlikely(cpu != WORK_CPU_UNBOUND)) @@ -2997,7 +2998,7 @@ bool flush_delayed_work(struct delayed_work *dwork) { local_irq_disable(); if (del_timer_sync(&dwork->timer)) - __queue_work(WORK_CPU_UNBOUND, + __queue_work(dwork->cpu, get_work_cwq(&dwork->work)->wq, &dwork->work); local_irq_enable(); return flush_work(&dwork->work); @@ -3020,7 +3021,7 @@ bool flush_delayed_work_sync(struct delayed_work *dwork) { local_irq_disable(); if (del_timer_sync(&dwork->timer)) - __queue_work(WORK_CPU_UNBOUND, + __queue_work(dwork->cpu, get_work_cwq(&dwork->work)->wq, &dwork->work); local_irq_enable(); return flush_work_sync(&dwork->work); -- 2.20.1