Commit 930c2ea5 authored by Marco Crivellari's avatar Marco Crivellari Committed by Tejun Heo
Browse files

workqueue: Add new WQ_PERCPU flag 



Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.

This patch adds a new WQ_PERCPU flag to explicitly request the use of
the per-CPU behavior. Both flags coexist for one release cycle to allow
callers to transition their calls.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

tj: Merged doc patch.

Suggested-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarMarco Crivellari <marco.crivellari@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 128ea9f6

Documentation/core-api/workqueue.rst

+6 −0
Original line number Diff line number Diff line
@@ -183,6 +183,12 @@ resources, scheduled and executed. 
  BH work items cannot sleep. All other features such as delayed queueing,

  flushing and canceling are supported.



``WQ_PERCPU``

  Work items queued to a per-cpu wq are bound to a specific CPU.

  This flag is the right choice when cpu locality is important.



  This flag is the complement of ``WQ_UNBOUND``.



``WQ_UNBOUND``

  Work items queued to an unbound wq are served by the special

  worker-pools which host workers which are not bound to any

include/linux/workqueue.h

+1 −0
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@@ -401,6 +401,7 @@ enum wq_flags { 
	 * http://thread.gmane.org/gmane.linux.kernel/1480396

	 */

	WQ_POWER_EFFICIENT	= 1 << 7,

	WQ_PERCPU		= 1 << 8, /* bound to a specific cpu */



	__WQ_DESTROYING		= 1 << 15, /* internal: workqueue is destroying */

	__WQ_DRAINING		= 1 << 16, /* internal: workqueue is draining */