Messages in this thread | | | Date | Thu, 4 Jan 2007 17:32:16 +0530 | From | Srivatsa Vaddagiri <> | Subject | Re: [PATCH, RFC] reimplement flush_workqueue() |
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On Mon, Dec 18, 2006 at 01:34:16AM +0300, Oleg Nesterov wrote: > void fastcall flush_workqueue(struct workqueue_struct *wq) > { > - might_sleep(); > - > + mutex_lock(&workqueue_mutex); > if (is_single_threaded(wq)) { > /* Always use first cpu's area. */ > - flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu), > - -1); > + flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu)); > } else { > int cpu; > > - mutex_lock(&workqueue_mutex); > for_each_online_cpu(cpu)
Can compiler optimizations lead to cpu_online_map being cached in a register while running this loop? AFAICS cpu_online_map is not declared to be volatile. If it can be cached, then we have the danger of invoking flush_cpu_workqueue() on a dead cpu (because flush_cpu_workqueue drops workqueue_mutex, cpu hp events can change cpu_online_map while we are in flush_cpu_workqueue).
> - flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu), cpu); > - mutex_unlock(&workqueue_mutex); > + flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
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