On Thu, Dec 14, 2006 at 12:13:16AM +0100, Ingo Molnar wrote:
> there's another bug as well: in schedule() resched_cpu() is called with
> the current runqueue held in two places, which is deadlock potential.
resched_cpu() was getting called after prepare_task_switch() which
releases the current runqueue lock. Isn't it?
> The easiest fix for this is to use trylock - find the patch for that.
> This is a hint only anyway - and if a CPU is idle its runqueue will be
Though I don't see a potential deadlock, I like this optimization.
thanks,
suresh
> lockable. (fixing it via double-locking is easy in the first call site,
> but the second one looks harder)
>
> Ingo
>
> Index: linux/kernel/sched.c
> ===================================================================
> --- linux.orig/kernel/sched.c
> +++ linux/kernel/sched.c
> @@ -1167,12 +1167,14 @@ static void resched_task(struct task_str
> if (!tsk_is_polling(p))
> smp_send_reschedule(cpu);
> }
> +
> static void resched_cpu(int cpu)
> {
> struct rq *rq = cpu_rq(cpu);
> - unsigned int flags;
> + unsigned long flags;
>
> - spin_lock_irqsave(&rq->lock, flags);
> + if (!spin_trylock_irqsave(&rq->lock, flags))
> + return;
> resched_task(cpu_curr(cpu));
> spin_unlock_irqrestore(&rq->lock, flags);
> }
-
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