On Thu, 2003-09-11 at 23:50, kkonaka@mac.com wrote:
> howdy,
>
> suppose I have a (character) driver code,
>
> does the following piece of code break under preemptive
> kernel option enabled? -- is there any pointer regarding
> precisely when kernel preemption can take place?
>
> TIA
> kenji
>
> --
> int busy = 0;
> wait_queue_head_t q;
> some_resource res; /* data structure shared between processes */
>
> ssize_t my_write(struct file * file, const char * buf,
> size_t count, loff_t *ppos)
> {
> while (busy) { /* grab exclusive access */
> interruptible_sleep_on(&q);
> }
>
> <do something assuming exclusive access to resources>
>
> busy = 0; /* release exclusive access */
> wake_up_interruptible(&q);
> return retval;
this code already breaks even without a non-preemptible kernel.....
your use of *_sleep_on() is defective.
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