Messages in this thread | | | Date | Thu, 2 Dec 2004 19:08:23 -0800 | From | Andrew Morton <> | Subject | Re: do_posix_clock_monotonic_gettime() returns negative nsec |
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Herbert Poetzl <herbert@13thfloor.at> wrote: > > > 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++; > }
Doesn't this imply that do_posix_clock_monotonic_gettime_parts() is returning a negative tv_nsec?
If so, that would point back at getnstimeofday(). What is your setting of CONFIG_TIME_INTERPOLATION? - 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/
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