On Tue, Aug 25, 2015 at 03:59:54PM +0800, Wanpeng Li wrote:
> +++ b/kernel/cpuset.c
> @@ -2376,8 +2376,12 @@ void cpuset_cpus_allowed(struct task_struct *tsk,
> struct cpumask *pmask)
>
> void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
> {
> + unsigned long flags;
> +
> rcu_read_lock();
> + raw_spin_lock_irqsave(&tsk->pi_lock, flags);
> do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
> + raw_spin_lock_irqsave(&tsk->pi_lock, flags);
> rcu_read_unlock();
Aside from the double lock thing that was already pointed out, I think
this is wrong, because the select_task_rq() call can already have
pi_lock held.
Taking it again would result in a deadlock.
Consider for instance:
try_to_wake_up()
raw_spin_lock_irqsave(->pi_lock)
select_task_rq()
select_ballback_rq()
cpuset_cpus_allowed_fallback()
raw_spin_lock_irqsave(->pi_lock)
The problem is with the migration path and should be fixed there.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
