From: Hillf Danton <hdanton@xxxxxxxx>
commit aa202f1f56960c60e7befaa0f49c72b8fa11b0a8 upstream.
wq_select_unbound_cpu() is designed for unbound workqueues only, but
it's wrongly called when using a bound workqueue too.
Fixing this ensures work queued to a bound workqueue with
cpu=WORK_CPU_UNBOUND always runs on the local CPU.
Before, that would happen only if wq_unbound_cpumask happened to include
it (likely almost always the case), or was empty, or we got lucky with
forced round-robin placement. So restricting
/sys/devices/virtual/workqueue/cpumask to a small subset of a machine's
CPUs would cause some bound work items to run unexpectedly there.
Fixes: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs")
Cc: stable@xxxxxxxxxxxxxxx # v4.5+
Signed-off-by: Hillf Danton <hdanton@xxxxxxxx>
[dj: massage changelog]
Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1417,14 +1417,16 @@ static void __queue_work(int cpu, struct
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
