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Commit 4857339d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'timers-fixes-for-linus' of... 

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
parents 0efcafb0 6c9bacb4

kernel/posix-cpu-timers.c

+1 −1
Original line number Diff line number Diff line
@@ -311,7 +311,7 @@ static int cpu_clock_sample_group(const clockid_t which_clock, 
	struct task_cputime cputime;



	thread_group_cputime(p, &cputime);

	switch (which_clock) {

	switch (CPUCLOCK_WHICH(which_clock)) {

	default:

		return -EINVAL;

	case CPUCLOCK_PROF:

kernel/time/timekeeping.c

+22 −0
Original line number Diff line number Diff line
@@ -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.

	 */