Re: Wait queue problem

[Ralf Baechle <ralf@oss.sgi.com>]

On Wed, Apr 17, 2002 at 12:03:19PM +0200, Andre.Messerschmidt@infineon.com 
wrote:

> Does anybody else have problems using wait queues in a 2.4.5 MIPS kernel?
> When I try to wake up a process from an interrupt it won't start to execute.
> It always waits for the timeout before resuming work. 
> In principal my code look like this:
> 
> wait_queue_head_t wq;
> 
> foo() {
> init_waitqueue_head(&wq);
> interruptible_sleep_on_timeout(&wq,10*HZ);
> }
> 
> foo_int() {
> wake_up_interuptible(&wq);
> }
> 
> Am I missing something? 

A bad race condition in that code.  If foo_int is called before your process
had a chance to get to sleep it'll never be woken before the timeout.

  Ralf