Messages in this thread | | | Date | Fri, 7 Aug 2015 11:16:08 -0400 | From | Tejun Heo <> | Subject | Re: [RFC][PATCH 1/4] sched: Fix a race between __kthread_bind() and sched_setaffinity() |
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On Fri, Aug 07, 2015 at 04:27:08PM +0200, Peter Zijlstra wrote: > Which is the rescue thread attaching itself to a pool that needs help, > and obviously the rescue thread isn't new so kthread_bind doesn't work > right. > > The best I could come up with is something like the below on top; does > that work for you? I'll go give it some runtime. > > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -1622,11 +1622,15 @@ static struct worker *alloc_worker(int n > * cpu-[un]hotplugs. > */ > static void worker_attach_to_pool(struct worker *worker, > - struct worker_pool *pool) > + struct worker_pool *pool, > + bool new) > { > mutex_lock(&pool->attach_mutex); > > - kthread_bind_mask(worker->task, pool->attrs->cpumask); > + if (new) > + kthread_bind_mask(worker->task, pool->attrs->cpumask); > + else > + set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); > > /* > * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains > @@ -1712,7 +1716,7 @@ static struct worker *create_worker(stru > set_user_nice(worker->task, pool->attrs->nice); > > /* successful, attach the worker to the pool */ > - worker_attach_to_pool(worker, pool); > + worker_attach_to_pool(worker, pool, true); > > /* start the newly created worker */ > spin_lock_irq(&pool->lock); > @@ -2241,7 +2245,7 @@ static int rescuer_thread(void *__rescue > > spin_unlock_irq(&wq_mayday_lock); > > - worker_attach_to_pool(rescuer, pool); > + worker_attach_to_pool(rescuer, pool, false);
Hmmm... the race condition didn't exist for workqueue in the first place, right? As long as the flag is set before the affinity is configured, there's no race condition. I think the code was better before. Can't we just revert workqueue.c part?
Thanks.
-- tejun
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