lkml.org 
[lkml]   [2004]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subjectdo_posix_clock_monotonic_gettime() returns negative nsec

Hi Folks!

recent kernels (tested 2.6.10-rc2 and 2.6.10-rc2-bk15)
produce funny output in /proc/uptime like this:

# cat /proc/uptime
12.4294967218 9.05
# cat /proc/uptime
13.4294967251 10.33
# cat /proc/uptime
14.4294967295 11.73

a short investigation of the issue, ended at
do_posix_clock_monotonic_gettime() which can (and
often does) return negative nsec values (within
one second), so while the actual 'time' returned
is correct, some parts of the kernel assume that
those part is within the range (0 - NSEC_PER_SEC)

len = sprintf(page,"%lu.%02lu %lu.%02lu\n",
(unsigned long) uptime.tv_sec,
(uptime.tv_nsec / (NSEC_PER_SEC / 100)),

as the function itself corrects overflows, it would
make sense to me to correct underflows too, for
example with the following patch:

--- ./kernel/posix-timers.c.orig 2004-11-19 21:11:05.000000000 +0100
+++ ./kernel/posix-timers.c 2004-12-03 02:23:56.000000000 +0100
@@ -1208,7 +1208,10 @@ int do_posix_clock_monotonic_gettime(str
tp->tv_sec += wall_to_mono.tv_sec;
tp->tv_nsec += wall_to_mono.tv_nsec;

- if ((tp->tv_nsec - NSEC_PER_SEC) > 0) {
+ if (tp->tv_nsec < 0) {
+ tp->tv_nsec += NSEC_PER_SEC;
+ tp->tv_sec--;
+ } else if ((tp->tv_nsec - NSEC_PER_SEC) > 0) {
tp->tv_nsec -= NSEC_PER_SEC;
tp->tv_sec++;
}
best,
Herbert

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:08    [W:0.053 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site