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Date: Tue, 8 Oct 2002 00:52:06 +0200 (CEST)
From: Rui Sousa <rui.sousa@laposte.net>
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To: Amol Lad <dal_loma@yahoo.com>
cc: linux-kernel@vger.kernel.org
Subject: Re: wake_up from interrupt handler
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On Mon, 7 Oct 2002, Amol Lad wrote:

> Hi,
>  I have a kernel thread which did add_to_wait_queue()
> to wait for an event. 
> The event for which above thread is waiting occurs in
> an interrupt handler that calls wake_up() to wake the
> above thread. 
> Now I am faced with a 'lost wakeup' problem, in which
> the    
> kernel thread checks whether event occured, he finds
> it to be 'not-occured' but before calling
> add_to_wait_queue(), interrupt handler detects that
> the event has occured and calls wake_up().
> My thread sleeps forever.

I believe the solution is to simply add_to_wait_queue()
_before_ checking the condition. If the signal arrives between
checking the condition and going to sleep your task will be
immediately awoken.

Rui Sousa

> I know some new APIs are provided in recent 2.5
> kernel, but how to avoid this in 2.4.18
>
> please CC me 
> 
> Thanks
> Amol
> 
> 
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