lkml.org 
[lkml]   [2000]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: jiffies wrap question...
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)>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:45    [W:0.055 / U:0.080 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site