60c057bca2
To avoid executing the same work item from multiple CPUs concurrently, a work_struct records the last pool it was on in its ->data so that, on the next queueing, the pool can be queried to determine whether the work item is still executing or not. A delayed_work goes through timer before actually being queued on the target workqueue and the timer needs to know the target workqueue and CPU. This is currently achieved by modifying delayed_work->work.data such that it points to the cwq which points to the target workqueue and the last CPU the work item was on. __queue_delayed_work() extracts the last CPU from delayed_work->work.data and then combines it with the target workqueue to create new work.data. The only thing this rather ugly hack achieves is encoding the target workqueue into delayed_work->work.data without using a separate field, which could be a trade off one can make; unfortunately, this entangles work->data management between regular workqueue and delayed_work code by setting cwq pointer before the work item is actually queued and becomes a hindrance for further improvements of work->data handling. This can be easily made sane by adding a target workqueue field to delayed_work. While delayed_work is used widely in the kernel and this does make it a bit larger (<5%), I think this is the right trade-off especially given the prospect of much saner handling of work->data which currently involves quite tricky memory barrier dancing, and don't expect to see any measureable effect. Add delayed_work->wq and drop the delayed_work->work.data overloading. tj: Rewrote the description. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> |
||
|---|---|---|
| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| keys | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| video | ||
| xen | ||
| Kbuild | ||