The following is a piece of code from the latter half of
schedule_timeout, in kernel/sched.c. Is it possible that
schedule_timeout could return an incorrect value, if the jiffy value
wraps between the first and last lines shown below.
expire = timeout + jiffies;
init_timer(&timer);
timer.expires = expire;
timer.data = (unsigned long) current;
timer.function = process_timeout;
add_timer(&timer);
schedule();
del_timer_sync(&timer);
timeout = expire - jiffies;
--
Jeff Garzik |
Building 1024 | Would you like a Twinkie?
MandrakeSoft |
On Fri, Nov 10, 2000 at 02:21:28AM -0500, Jeff Garzik wrote:
> The following is a piece of code from the latter half of
> schedule_timeout, in kernel/sched.c. Is it possible that
> schedule_timeout could return an incorrect value, if the jiffy value
> wraps between the first and last lines shown below.
let's say the first line happens n ticks before the wrap and the second,
m ticks afterwards.
> expire = timeout + jiffies;
expire = timeout + 2^32/2^64 - n = timeout - n
> timeout = expire - jiffies;
timeout = expire - m = timeout - n - m = timeout - (n+m)
(n+m) is the time that actually passed while we were asleep, and timeout
has the correct value (timeout - ticks that happened)>