Re: Problems writting a CHAR Driver with interruptible_sleep (wait_

Raul Dias (chaos@swi.com.br)
Mon, 16 Aug 1999 10:48:21 -0300 (EST)

On 14 Aug, Benjamin LaHaise wrote:
> struct wait_queue *my_wait_queue = NULL;
>
> foo_irq()
> {
> wake_up_interruptible(&my_wait_queue);
> }
>
> foo_read()
> {
> struct wait_queue wait = { current, NULL };
>
> current->state = TASK_INTERRUPTIBLE;
> add_wait_queue(&my_wait_queue, &wait);
>
> /* now start the hardware. if the interrupt comes in before we
> * enter schedule, the task is set back to TASK_RUNNING and the
> * schedule becomes a no-op
> */
> ...
>
> schedule();
> if (signal_pending(current))
> ret = -ERESTARTSYS;
>
> ...cleanup
>
> remove_wait_queue(&my_wait_queue, &wait);
> return ret;
> }

hi,

This implementation worked for a while until I discover a Hardware
problem.
Sometimes the hardware fails to generate the interrupt.

So I changed:
schedule(); to schedule_timeout(1);

But 1 jiffie (0.1 secs) is too long!

Is there a way to specify a timeout value of 100 microseconds?

This is the last one:

Can I count the time with a higher precision than with jiffies?
I need to keep track of the time on every read, but a jiffie is too
slow.

Best Regards,

Raul Dias

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