Commit 2c1aca4b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-5.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 

Pull workqueue fixes from Tejun Heo:
 "Workqueue has been incorrectly round-robining per-cpu work items.
  Hillf's patch fixes that.

  The other patch documents memory-ordering properties of workqueue
  operations"

* 'for-5.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: don't use wq_select_unbound_cpu() for bound works
  workqueue: Document (some) memory-ordering properties of {queue,schedule}_work()
parents 30bb5572 aa202f1f

include/linux/workqueue.h

+16 −0
Original line number Diff line number Diff line
@@ -487,6 +487,19 @@ extern void wq_worker_comm(char *buf, size_t size, struct task_struct *task); 
 *

 * We queue the work to the CPU on which it was submitted, but if the CPU dies

 * it can be processed by another CPU.

 *

 * Memory-ordering properties:  If it returns %true, guarantees that all stores

 * preceding the call to queue_work() in the program order will be visible from

 * the CPU which will execute @work by the time such work executes, e.g.,

 *

 * { x is initially 0 }

 *

 *   CPU0				CPU1

 *

 *   WRITE_ONCE(x, 1);			[ @work is being executed ]

 *   r0 = queue_work(wq, work);		  r1 = READ_ONCE(x);

 *

 * Forbids: r0 == true && r1 == 0

 */

static inline bool queue_work(struct workqueue_struct *wq,

			      struct work_struct *work)
@@ -546,6 +559,9 @@ static inline bool schedule_work_on(int cpu, struct work_struct *work) 
 * This puts a job in the kernel-global workqueue if it was not already

 * queued and leaves it in the same position on the kernel-global

 * workqueue otherwise.

 *

 * Shares the same memory-ordering properties of queue_work(), cf. the

 * DocBook header of queue_work().

 */

static inline bool schedule_work(struct work_struct *work)

{

kernel/workqueue.c

+8 −6
Original line number Diff line number Diff line
@@ -1411,14 +1411,16 @@ static void __queue_work(int cpu, struct workqueue_struct *wq, 
		return;

	rcu_read_lock();

retry:

	/* pwq which will be used unless @work is executing elsewhere */

	if (wq->flags & WQ_UNBOUND) {

		if (req_cpu == WORK_CPU_UNBOUND)

			cpu = wq_select_unbound_cpu(raw_smp_processor_id());



	/* pwq which will be used unless @work is executing elsewhere */

	if (!(wq->flags & WQ_UNBOUND))

		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);

	else

		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));

	} else {

		if (req_cpu == WORK_CPU_UNBOUND)

			cpu = raw_smp_processor_id();

		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);

	}



	/*

	 * If @work was previously on a different pool, it might still be