Wait queue problem

Wait queue problem

[Andre.Messerschmidt]

Hi,

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? 

best regards
--
Andre Messerschmidt

Application Engineer
Infineon Technologies AG

Re: Wait queue problem

[Ralf Baechle]

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

Re: Wait queue problem

[Richard Hodges]

> 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? 

On Thu, 18 Apr 2002, Ralf Baechle wrote:
 
> 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.

That reminds me :-)  

I have looked around for a version of wait_event_interruptible() that
has a timeout (starting my search in sched.h of course).  Before I get
around to writing my own, does anyone have one already?

Thanks,

-Richard

Re: Wait queue problem

[Misbah khan]

I guess that you are missing one more condition the flag bit which you need
to set and reset accordingly in the function and in the interrupt handler 

interruptible_sleep_on_timeout(&wq,flag!=0,10*HZ);

Try out this for any query please let me know 

regard 
misbah



Andre.Messerschmidt wrote:
> 
> Hi,
> 
> 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? 
> 
> best regards
> --
> Andre Messerschmidt
> 
> Application Engineer
> Infineon Technologies AG
> 
> 
> 
> 

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