Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 11/15] workqueue: reorganize try_to_grab_pending() and __cancel_timer_work() | Date | Fri, 27 Jul 2012 16:55:04 -0700 |
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* 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.
Signed-off-by: Tejun Heo <tj@kernel.org> --- kernel/workqueue.c | 36 +++++++++++++++++++++++++----------- 1 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 358779c..a0eb033 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1004,15 +1004,29 @@ 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 + * + * 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, + struct timer_list *timer) { struct global_cwq *gcwq; - int ret = -1; + /* try to steal the timer if it exists */ + if (timer && likely(del_timer(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 +1036,7 @@ 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 +1052,14 @@ 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; } /** @@ -2823,9 +2839,7 @@ static bool __cancel_work_timer(struct work_struct *work, int ret; do { - ret = (timer && likely(del_timer(timer))); - if (!ret) - ret = try_to_grab_pending(work); + ret = try_to_grab_pending(work, timer); wait_on_work(work); } while (unlikely(ret < 0)); -- 1.7.7.3
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