Messages in this thread | | | Date | Thu, 4 Jan 2007 17:38:56 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH, RFC] reimplement flush_workqueue() |
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On 01/04, Srivatsa Vaddagiri wrote: > > 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.
But it is not const either,
> If it can be cached,
I believe this would be a compiler's bug. Let's take a more simple example,
while (!condition) schedule();
What if compiler will cache the value of global 'condition' ?
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).
Oleg.
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