diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-12-04 21:40:29 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-12-04 21:40:29 -0800 |
commit | 4857339d7c01cd81ce8872da2d1f9183b07b1c87 (patch) | |
tree | 49d311b8bd623810822106a706f9db886c6ffb07 /kernel/time/timekeeping.c | |
parent | 0efcafb0fb7a163999a8821e8a5e7792fca90a2d (diff) | |
parent | 6c9bacb41c10ba84ff68f238e234d96f35fb64f7 (diff) |
Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
time: catch xtime_nsec underflows and fix them
posix-cpu-timers: fix clock_gettime with CLOCK_PROCESS_CPUTIME_ID
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r-- | kernel/time/timekeeping.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index e7acfb482a6..fa05e88aa76 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -518,6 +518,28 @@ void update_wall_time(void) /* correct the clock when NTP error is too big */ clocksource_adjust(offset); + /* + * Since in the loop above, we accumulate any amount of time + * in xtime_nsec over a second into xtime.tv_sec, its possible for + * xtime_nsec to be fairly small after the loop. Further, if we're + * slightly speeding the clocksource up in clocksource_adjust(), + * its possible the required corrective factor to xtime_nsec could + * cause it to underflow. + * + * Now, we cannot simply roll the accumulated second back, since + * the NTP subsystem has been notified via second_overflow. So + * instead we push xtime_nsec forward by the amount we underflowed, + * and add that amount into the error. + * + * We'll correct this error next time through this function, when + * xtime_nsec is not as small. + */ + if (unlikely((s64)clock->xtime_nsec < 0)) { + s64 neg = -(s64)clock->xtime_nsec; + clock->xtime_nsec = 0; + clock->error += neg << (NTP_SCALE_SHIFT - clock->shift); + } + /* store full nanoseconds into xtime after rounding it up and * add the remainder to the error difference. */ |