Messages in this thread | | | Subject | Re: do_posix_clock_monotonic_gettime() returns negative nsec | From | john stultz <> | Date | Thu, 02 Dec 2004 19:00:51 -0800 |
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On Thu, 2004-12-02 at 18:03, Herbert Poetzl wrote: > 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++; > }
Sounds like its a good fix to me.
George: You have any comment?
thanks -john
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