Messages in this thread Patch in this message |  | | Date | Wed, 6 Feb 2013 16:53:02 -0800 | From | Tejun Heo <> | Subject | [PATCH wq/for-3.9] workqueue: make work->data point to pool after try_to_grab_pending() |
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From: Lai Jiangshan <laijs@cn.fujitsu.com>
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 <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> --- kernel/workqueue.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -556,6 +556,13 @@ static void set_work_cwq(struct work_str 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 wo 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; }
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