Messages in this thread | | | Date | Tue, 02 Mar 2010 00:32:18 +0900 | From | Tejun Heo <> | Subject | Re: [PATCH 16/43] workqueue: kill cpu_populated_map |
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Hello,
On 03/01/2010 01:00 AM, Oleg Nesterov wrote: > On 02/26, Tejun Heo wrote: >> >> @@ -1023,41 +991,40 @@ struct workqueue_struct *__create_workqueue_key(const char *name, >> ... >> + cpu_maps_update_done(); >> ... >> + >> + spin_lock(&workqueue_lock); >> + list_add(&wq->list, &workqueues); >> + spin_unlock(&workqueue_lock); > > OK, but if cpu_up() happens right after we drop cpu_maps_update_done(), > cwq->thread on the new CPU will run unbound?
Indeed, looks like I was too impatient with cpu_maps_update_done().
>> @@ -1127,47 +1091,30 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, >> ... >> list_for_each_entry(wq, &workqueues, list) { > > this becomes unsafe. create/destroy can modify workqueues list > in parallel.
Yeap, has always been like that. Will be fixed by later changes.
>> case CPU_ONLINE: >> - start_workqueue_thread(cwq, cpu); >> + __set_cpus_allowed(cwq->thread, get_cpu_mask(cpu), >> + true); > > if the thread doesn't have PF_THREAD_BOUND, who will set it?
Indeed will update the worker function to set PF_THREAD_BOUND itself but again this problem is gone with later patches.
>> case CPU_POST_DEAD: >> - cleanup_workqueue_thread(cwq); >> + lock_map_acquire(&cwq->wq->lockdep_map); >> + lock_map_release(&cwq->wq->lockdep_map); >> + flush_cpu_workqueue(cwq); > > This can race with destroy_workqueue(), no?
Yes, it can and, again, has been always like that and will be fixed by later patches.
> I guess this patch is preparation, probably these problems should > go away later...
I'll fix the new problems but leave the existing ones alone. I don't think it's worth fixing them at this point with all the pending changes.
Thanks.
-- tejun
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