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SubjectRe: [BUG -rt] scheduling in atomic.

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Ingo,
>
> I've hit this. I compiled the kernel as CONFIG_PREEMPT, and turned off
> IRQ's as threads.
>
> BUG: scheduling while atomic: swapper/0x00000001/1, CPU#3

> int filevec_add_drain_all(void)
> {
> return schedule_on_each_cpu(filevec_add_drain_per_cpu, NULL);
> }
>
>
> And schedule_on_each_cpu is easily schedulable.
>
> So it seems that it schedules while holding a spin lock.

hm, indeed. I've Cc:-ed Pete who wrote the file-lock scalability
patchset. My quick impression is that taking the workqueue_mutex in
schedule_on_each_cpu() is unwarranted - i.e. the patch below should fix
it.

Ingo

Index: linux/kernel/workqueue.c
===================================================================
--- linux.orig/kernel/workqueue.c
+++ linux/kernel/workqueue.c
@@ -564,15 +564,15 @@ int schedule_on_each_cpu(void (*func)(vo
if (!works)
return -ENOMEM;

- mutex_lock(&workqueue_mutex);
for_each_online_cpu(cpu) {
INIT_WORK(per_cpu_ptr(works, cpu), func, info);
__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
per_cpu_ptr(works, cpu));
}
- mutex_unlock(&workqueue_mutex);
flush_workqueue(keventd_wq);
+
free_percpu(works);
+
return 0;
}

-
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