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Date: Fri, 3 Oct 2003 13:36:32 -0700
From: Andrew Morton <akpm@osdl.org>
To: Matthew Wilcox <willy@debian.org>
Cc: umka@namesys.com, acpi-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
Subject: Re: down_timeout
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Matthew Wilcox <willy@debian.org> wrote:
>
> /* Returns -EINTR if the timeout expires */
> int down_timeout(struct semaphore *sem, long timeout)
> {
> 	struct timer_list timer;
> 	int result;
> 
> 	init_timer(&timer);
> 	timer.expires = timeout + jiffies;
> 	timer.data = (unsigned long) current;
> 	timer.function = process_timeout;
> 
> 	add_timer(&timer);
> 	result = down_interruptible(sem);
> 	del_timer_sync(&timer);
> 
> 	return result;
> }

down_interruptible() will only break out if signal_pending(current), so the
wakeup-on-expiry here will not work as desired.

New per-arch primitives would be needed to implement this, I think.