On Thu, Dec 07, 2006 at 11:37:00AM -0800, Andrew Morton wrote:
> -static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
> +/*
> + * If cpu == -1 it's a single-threaded workqueue and the caller does not hold
> + * workqueue_mutex
> + */
> +static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq, int cpu)
Lets say @cpu = 4
> {
> if (cwq->thread == current) {
> /*
> * Probably keventd trying to flush its own queue. So simply run
> * it by hand rather than deadlocking.
> */
> + if (cpu != -1)
> + mutex_unlock(&workqueue_mutex);
Lets say we release the workqueue mutex here (events/4 is trying to
flush its own workqueue). Immediately another CPU takes this mutex
(in CPU_DOWN_PREPARE) and brings down CPU4. In CPU_DEAD handling we now wait
on events/4 thread to exit (cleanup_workqueue_thread).
Couldnt this wait deadlock on :
> run_workqueue(cwq);
> + if (cpu != -1)
> + mutex_lock(&workqueue_mutex);
events/4 thread itself wanting the same mutex above?
What am I missing?
--
Regards,
vatsa
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