Re: timing out on a semaphore

[Andrew Morton]

Tim Waugh wrote:
> 
> I'm trying to chase down a semaphore time-out problem.  I want to
> sleep on a semaphore until either
> 
> (a) it's signalled, or
> (b) some amount of time has elapsed.
> 
> What I'm doing is calling add_timer, and then down_interruptible, and
> finally del_timer.  The timer's function ups the semaphore.
> 
> The code is in parport_wait_event, in drivers/parport/ieee1284.c.
> 
> Can anyone see anything obviously wrong with it?  It seems to
> sometimes get stuck.

I think there might be a bogon in __down_interruptible's
handling of the semaphore state in this case.  I remember
spotting something a few months back but I can't immediately
remember what it was :(

I'd suggest you slot a

	sema_init(&port->physport->ieee1284.irq, 1);

into parport_wait_event() prior to adding the timer.  If that
fixes it I'll go back through my patchpile, see if I can
resurrect that grey cell.

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