Re: [PATCH] Export current_is_keventd() for libphy

Andrew Morton
2006-12-05T19:31:34Z

On Tue, 5 Dec 2006 10:07:21 -0800 (PST)
Linus Torvalds <torvalds@osdl.org> wrote:

>
>
> On Tue, 5 Dec 2006, Maciej W. Rozycki wrote:
> >
> > One way of avoiding it is calling flush_scheduled_work() from
> > phy_stop_interrupts(). This is fine as long as a caller of
> > phy_stop_interrupts() (not necessarily the immediate one calling into
> > libphy) does not hold the netlink lock.
> >
> > If a caller indeed holds the netlink lock, then a driver effectively
> > calling phy_stop_interrupts() may arrange for the function to be itself
> > scheduled through the event queue. This has the effect of avoiding the
> > race as well, as the queue is processed in order, except it causes more
> > hassle for the driver.
>
> I would personally be ok with "flush_scheduled_work()" _itself_ noticing
> that it is actually waiting to flush "itself", and just being a no-op in
> that case.

It does do that:

static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
{
if (cwq->thread == current) {
/*
* Probably keventd trying to flush its own queue. So simply run
* it by hand rather than deadlocking.
*/
run_workqueue(cwq);