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sched: fix prev_stime calculation

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Srivatsa Vaddagiri noticed occasionally incorrect CPU usage
values in top and tracked it down to stime going below 0 in
task_stime(). Negative values are possible there due to the
sampled nature of stime/utime.

Fix suggested by Balbir Singh.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
This commit is contained in:
Ingo Molnar 2007-11-26 21:21:49 +01:00
parent 5e8869bb69
commit 08e4570a4a
1 changed files with 3 additions and 1 deletions
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4
fs/proc/array.c
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@ -374,7 +374,9 @@ static cputime_t task_stime(struct task_struct *p)
stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
cputime_to_clock_t(task_utime(p));
p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
if (stime >= 0)
p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
return p->prev_stime;
}
#endif