From 36e227d242f9ec7cb4a8e968561b3b26e3d8b5d1 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 3 Aug 2012 10:30:46 -0700 Subject: [PATCH] workqueue: reorganize try_to_grab_pending() and __cancel_timer_work() * Use bool @is_dwork instead of @timer and let try_to_grab_pending() use to_delayed_work() to determine the delayed_work address. * Move timer handling from __cancel_work_timer() to try_to_grab_pending(). * Make try_to_grab_pending() use -EAGAIN instead of -1 for busy-looping and drop the ret local variable. * Add proper function comment to try_to_grab_pending(). This makes the code a bit easier to understand and will ease further changes. This patch doesn't make any functional change. v2: Use @is_dwork instead of @timer. Signed-off-by: Tejun Heo --- kernel/workqueue.c | 47 +++++++++++++++++++++++++++++++--------------- 1 file changed, 32 insertions(+), 15 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index d7f1b7e2bba..4b3663b1c67 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1004,15 +1004,33 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color, complete(&cwq->wq->first_flusher->done); } -/* - * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, - * so this work can't be re-armed in any way. +/** + * try_to_grab_pending - steal work item from worklist + * @work: work item to steal + * @is_dwork: @work is a delayed_work + * + * Try to grab PENDING bit of @work. This function can handle @work in any + * stable state - idle, on timer or on worklist. Return values are + * + * 1 if @work was pending and we successfully stole PENDING + * 0 if @work was idle and we claimed PENDING + * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry + * + * On >= 0 return, the caller owns @work's PENDING bit. */ -static int try_to_grab_pending(struct work_struct *work) +static int try_to_grab_pending(struct work_struct *work, bool is_dwork) { struct global_cwq *gcwq; - int ret = -1; + /* try to steal the timer if it exists */ + if (is_dwork) { + struct delayed_work *dwork = to_delayed_work(work); + + if (likely(del_timer(&dwork->timer))) + return 1; + } + + /* try to claim PENDING the normal way */ if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) return 0; @@ -1022,7 +1040,7 @@ static int try_to_grab_pending(struct work_struct *work) */ gcwq = get_work_gcwq(work); if (!gcwq) - return ret; + return -EAGAIN; spin_lock_irq(&gcwq->lock); if (!list_empty(&work->entry)) { @@ -1038,12 +1056,14 @@ static int try_to_grab_pending(struct work_struct *work) cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work), *work_data_bits(work) & WORK_STRUCT_DELAYED); - ret = 1; + + spin_unlock_irq(&gcwq->lock); + return 1; } } spin_unlock_irq(&gcwq->lock); - return ret; + return -EAGAIN; } /** @@ -2817,15 +2837,12 @@ bool flush_work_sync(struct work_struct *work) } EXPORT_SYMBOL_GPL(flush_work_sync); -static bool __cancel_work_timer(struct work_struct *work, - struct timer_list* timer) +static bool __cancel_work_timer(struct work_struct *work, bool is_dwork) { int ret; do { - ret = (timer && likely(del_timer(timer))); - if (!ret) - ret = try_to_grab_pending(work); + ret = try_to_grab_pending(work, is_dwork); wait_on_work(work); } while (unlikely(ret < 0)); @@ -2853,7 +2870,7 @@ static bool __cancel_work_timer(struct work_struct *work, */ bool cancel_work_sync(struct work_struct *work) { - return __cancel_work_timer(work, NULL); + return __cancel_work_timer(work, false); } EXPORT_SYMBOL_GPL(cancel_work_sync); @@ -2914,7 +2931,7 @@ EXPORT_SYMBOL(flush_delayed_work_sync); */ bool cancel_delayed_work_sync(struct delayed_work *dwork) { - return __cancel_work_timer(&dwork->work, &dwork->timer); + return __cancel_work_timer(&dwork->work, true); } EXPORT_SYMBOL(cancel_delayed_work_sync); -- 2.20.1