diff options
| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2012-09-18 10:40:00 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-13 05:50:20 +0900 |
| commit | d024fea7032bc7c333c967db530b44d59a180d14 (patch) | |
| tree | 2deb7366049b81f19b2197c09af5d5297251ebc3 /kernel | |
| parent | d878ce75405d3fc90b0253d44ce603e5948584fb (diff) | |
workqueue: fix possible stall on try_to_grab_pending() of a delayed work item
commit 3aa62497594430ea522050b75c033f71f2c60ee6 upstream.
Currently, when try_to_grab_pending() grabs a delayed work item, it
leaves its linked work items alone on the delayed_works. The linked
work items are always NO_COLOR and will cause future
cwq_activate_first_delayed() increase cwq->nr_active incorrectly, and
may cause the whole cwq to stall. For example,
state: cwq->max_active = 1, cwq->nr_active = 1
one work in cwq->pool, many in cwq->delayed_works.
step1: try_to_grab_pending() removes a work item from delayed_works
but leaves its NO_COLOR linked work items on it.
step2: Later on, cwq_activate_first_delayed() activates the linked
work item increasing ->nr_active.
step3: cwq->nr_active = 1, but all activated work items of the cwq are
NO_COLOR. When they finish, cwq->nr_active will not be
decreased due to NO_COLOR, and no further work items will be
activated from cwq->delayed_works. the cwq stalls.
Fix it by ensuring the target work item is activated before stealing
PENDING in try_to_grab_pending(). This ensures that all the linked
work items are activated without incorrectly bumping cwq->nr_active.
tj: Updated comment and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index cb16c8a82a14..872bd6d9be2d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1927,10 +1927,9 @@ static void move_linked_works(struct work_struct *work, struct list_head *head, *nextp = n; } -static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) +static void cwq_activate_delayed_work(struct work_struct *work) { - struct work_struct *work = list_first_entry(&cwq->delayed_works, - struct work_struct, entry); + struct cpu_workqueue_struct *cwq = get_work_cwq(work); trace_workqueue_activate_work(work); move_linked_works(work, &cwq->pool->worklist, NULL); @@ -1938,6 +1937,14 @@ static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) cwq->nr_active++; } +static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) +{ + struct work_struct *work = list_first_entry(&cwq->delayed_works, + struct work_struct, entry); + + cwq_activate_delayed_work(work); +} + /** * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight * @cwq: cwq of interest @@ -2846,6 +2853,18 @@ static int try_to_grab_pending(struct work_struct *work) smp_rmb(); if (gcwq == get_work_gcwq(work)) { debug_work_deactivate(work); + + /* + * A delayed work item cannot be grabbed directly + * because it might have linked NO_COLOR work items + * which, if left on the delayed_list, will confuse + * cwq->nr_active management later on and cause + * stall. Make sure the work item is activated + * before grabbing. + */ + if (*work_data_bits(work) & WORK_STRUCT_DELAYED) + cwq_activate_delayed_work(work); + list_del_init(&work->entry); cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work), |