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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-03-10 14:48:22 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-03-10 14:48:22 -0700 |
commit | 2c1aca4bd3fefc57018773cc8771f71c9bfbdc1f (patch) | |
tree | d52c532985870176a65a0253ca5919bc8132063a | |
parent | Merge tag 'ktest-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-ktest (diff) | |
parent | workqueue: don't use wq_select_unbound_cpu() for bound works (diff) | |
download | wireguard-linux-2c1aca4bd3fefc57018773cc8771f71c9bfbdc1f.tar.xz wireguard-linux-2c1aca4bd3fefc57018773cc8771f71c9bfbdc1f.zip |
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()
-rw-r--r-- | include/linux/workqueue.h | 16 | ||||
-rw-r--r-- | kernel/workqueue.c | 14 |
2 files changed, 24 insertions, 6 deletions
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 4261d1c6e87b..e48554e6526c 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -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) { diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 301db4406bc3..4e01c448b4b4 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1411,14 +1411,16 @@ static void __queue_work(int cpu, struct workqueue_struct *wq, return; rcu_read_lock(); retry: - 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 + if (wq->flags & WQ_UNBOUND) { + if (req_cpu == WORK_CPU_UNBOUND) + cpu = wq_select_unbound_cpu(raw_smp_processor_id()); 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 |