Hello Rusty,
On Wed, Oct 24, 2007 at 05:21:04PM +1000, Rusty Russell wrote:
> On Wednesday 24 October 2007 15:37:16 Gautham R Shenoy wrote:
> > @@ -712,7 +712,7 @@ static void start_workqueue_thread(struc
> >
> > if (p != NULL) {
> > if (cpu >= 0)
> > - kthread_bind(p, cpu);
> > + set_cpus_allowed(p, cpumask_of_cpu(cpu));
> > wake_up_process(p);
> > }
>
> Hi Gautham!
>
> This works, although the change is unnecessary.
This change was necessary because once a cpu goes offline, the worker
threads for that particular cpu, sleep with their state being
TASK_INTERRUPTIBLE. Thus, during CPU_ONLINE, when we call
start_workqueue_thread(), kthread_bind() yells since the worker thread
is not TASK_UNINTERRUPTIBLE.
Probably later on when Oleg plans to re-introduce the ->should_stop
flag, we can put the worker threads to uninterruptible sleep, and revert
back to kthread_bind().
> If you're going to
> do this I'd prefer "if (set_cpus_allowed(p, cpumask_of_cpu(cpu)) != 0)
> BUG();".
Not sure if this is required. set_cpus_allowed() returns a non-zero
value only if the cpumask passed doesn't intersect with the cpu-online
map. In our case, start_workqueue_thread() is called only when the cpu
is online. i.e
a) __create_workqueue_key() calls start_workqueue_thread() with
get_online_cpus() protection only for those cpus which are online.
b) workqueue_cpu_callback() calls start_workqueue_thread() on event
of a CPU_ONLINE.
>
> Cheers,
> Rusty.
Thanks and Regards
gautham.
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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