From 4468a00fd9a274fe1b30c886370d662e4a439efb Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Wed, 6 Feb 2013 18:04:53 -0800 Subject: workqueue: make work->data point to pool after try_to_grab_pending() We plan to use work->data pointing to cwq as the synchronization invariant when determining whether a given work item is on a locked pool or not, which requires work->data pointing to cwq only while the work item is queued on the associated pool. With delayed_work updated not to overload work->data for target workqueue recording, the only case where we still have off-queue work->data pointing to cwq is try_to_grab_pending() which doesn't update work->data after stealing a queued work item. There's no reason for try_to_grab_pending() to not update work->data to point to the pool instead of cwq, like the normal execution does. This patch adds set_work_pool_and_keep_pending() which makes work->data point to pool instead of cwq but keeps the pending bit unlike set_work_pool_and_clear_pending() (surprise!). After this patch, it's guaranteed that only queued work items point to cwqs. This patch doesn't introduce any visible behavior change. tj: Renamed the new helper function to match set_work_pool_and_clear_pending() and rewrote the description. Signed-off-by: Lai Jiangshan Signed-off-by: Tejun Heo --- kernel/workqueue.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 41a502ce3802..1a442c301ddb 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -556,6 +556,13 @@ static void set_work_cwq(struct work_struct *work, WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); } +static void set_work_pool_and_keep_pending(struct work_struct *work, + int pool_id) +{ + set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, + WORK_STRUCT_PENDING); +} + static void set_work_pool_and_clear_pending(struct work_struct *work, int pool_id) { @@ -1115,6 +1122,9 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork, cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work)); + /* work->data points to cwq iff queued, point to pool */ + set_work_pool_and_keep_pending(work, pool->id); + spin_unlock(&pool->lock); return 1; } -- cgit v1.2.3