From: Oleg Nesterov Currently typeof(delayed_work->work.data) is "struct workqueue_struct" when the timer is pending "struct cpu_workqueue_struct" whe the work is queued This makes impossible to use flush_fork(delayed_work->work) in addition to cancel_delayed_work/cancel_rearming_delayed_work, not good. Change queue_delayed_work/delayed_work_timer_fn to use cwq, not wq. This complicates (and uglifies) these functions a little bit, but alows us to use flush_fork(dwork) and imho makes the whole code more consistent. Also, document the fact that cancel_rearming_delayed_work() doesn't garantee the completion of work->func() upon return. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton --- include/linux/workqueue.h | 2 +- kernel/workqueue.c | 28 ++++++++++++++++++---------- 2 files changed, 19 insertions(+), 11 deletions(-) diff -puN include/linux/workqueue.h~make-queue_delayed_work-friendly-to-flush_fork include/linux/workqueue.h --- a/include/linux/workqueue.h~make-queue_delayed_work-friendly-to-flush_fork +++ a/include/linux/workqueue.h @@ -193,7 +193,7 @@ int execute_in_process_context(work_func /* * Kill off a pending schedule_delayed_work(). Note that the work callback * function may still be running on return from cancel_delayed_work(). Run - * flush_scheduled_work() or flush_work() to wait on it. + * flush_workqueue() or flush_work() to wait on it. */ static inline int cancel_delayed_work(struct delayed_work *work) { diff -puN kernel/workqueue.c~make-queue_delayed_work-friendly-to-flush_fork kernel/workqueue.c --- a/kernel/workqueue.c~make-queue_delayed_work-friendly-to-flush_fork +++ a/kernel/workqueue.c @@ -90,18 +90,20 @@ static const cpumask_t *wq_cpu_map(struc * Set the workqueue on which a work item is to be run * - Must *only* be called if the pending flag is set */ -static inline void set_wq_data(struct work_struct *work, void *wq) +static inline void set_wq_data(struct work_struct *work, + struct cpu_workqueue_struct *cwq) { unsigned long new; BUG_ON(!work_pending(work)); - new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING); + new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING); new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work); atomic_long_set(&work->data, new); } -static inline void *get_wq_data(struct work_struct *work) +static inline +struct cpu_workqueue_struct *get_wq_data(struct work_struct *work) { return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK); } @@ -157,7 +159,8 @@ EXPORT_SYMBOL_GPL(queue_work); void delayed_work_timer_fn(unsigned long __data) { struct delayed_work *dwork = (struct delayed_work *)__data; - struct workqueue_struct *wq = get_wq_data(&dwork->work); + struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work); + struct workqueue_struct *wq = cwq->wq; int cpu = smp_processor_id(); if (unlikely(is_single_threaded(wq))) @@ -189,8 +192,9 @@ int fastcall queue_delayed_work(struct w BUG_ON(timer_pending(timer)); BUG_ON(!list_empty(&work->entry)); - /* This stores wq for the moment, for the timer_fn */ - set_wq_data(work, wq); + /* This stores cwq for the moment, for the timer_fn */ + set_wq_data(work, + per_cpu_ptr(wq->cpu_wq, raw_smp_processor_id())); timer->expires = jiffies + delay; timer->data = (unsigned long)dwork; timer->function = delayed_work_timer_fn; @@ -221,8 +225,9 @@ int queue_delayed_work_on(int cpu, struc BUG_ON(timer_pending(timer)); BUG_ON(!list_empty(&work->entry)); - /* This stores wq for the moment, for the timer_fn */ - set_wq_data(work, wq); + /* This stores cwq for the moment, for the timer_fn */ + set_wq_data(work, + per_cpu_ptr(wq->cpu_wq, raw_smp_processor_id())); timer->expires = jiffies + delay; timer->data = (unsigned long)dwork; timer->function = delayed_work_timer_fn; @@ -562,9 +567,12 @@ void flush_work_keventd(struct work_stru EXPORT_SYMBOL(flush_work_keventd); /** - * cancel_rearming_delayed_workqueue - reliably kill off a delayed work whose handler rearms the delayed work. + * cancel_rearming_delayed_workqueue - kill off a delayed work whose handler rearms the delayed work. * @wq: the controlling workqueue structure * @dwork: the delayed work struct + * + * Note that the work callback function may still be running on return from + * cancel_delayed_work(). Run flush_workqueue() or flush_work() to wait on it. */ void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq, struct delayed_work *dwork) @@ -579,7 +587,7 @@ void cancel_rearming_delayed_workqueue(s EXPORT_SYMBOL(cancel_rearming_delayed_workqueue); /** - * cancel_rearming_delayed_work - reliably kill off a delayed keventd work whose handler rearms the delayed work. + * cancel_rearming_delayed_work - kill off a delayed keventd work whose handler rearms the delayed work. * @dwork: the delayed work struct */ void cancel_rearming_delayed_work(struct delayed_work *dwork) _