Messages in this thread | | | Date | Tue, 19 Jul 2011 16:21:34 -0600 | From | Terry Loftin <> | Subject | Re: [PATCH 2/2] sched: Fix "divide error: 0000" in find_busiest_group |
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On 07/19/2011 03:18 PM, Peter Zijlstra wrote: > On Tue, 2011-07-19 at 14:58 -0600, Terry Loftin wrote: >> Add a check to sched_avg_update() to detect and reset age_stamp if the >> clock value has wrapped. Because __cycles_2_ns() includes an offset >> to account for start up time, the clock may not wrap to zero, so use >> the current clock value instead. > > So you're running on a platform (unspecified) where we use a raw > sched_clock() that is buggy. Again, you're fixing symptoms not causes. > This x86_64. This is the actual cause, unless the rq->clock value should never roll, in which case, the clock roll is the actual cause and you can disregard these patches.
-T >> Signed-off-by: Terry Loftin <terry.loftin@hp.com> >> Signed-off-by: Bob Montgomery <bob.montgomery@hp.com> >> --- >> diff --git a/kernel/sched.c b/kernel/sched.c >> index 18d38e4..b39cae1 100644 >> --- a/kernel/sched.c >> +++ b/kernel/sched.c >> @@ -1256,6 +1256,8 @@ static void sched_avg_update(struct rq *rq) >> { >> s64 period = sched_avg_period(); >> >> + if (unlikely(rq->age_stamp > rq->clock)) >> + rq->age_stamp = rq->clock; >> while ((s64)(rq->clock - rq->age_stamp) > period) { >> /* >> * Inline assembly required to prevent the compiler > > >
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