sched: Make sure to not re-read variables after validation
We could re-read rq->rt_avg after we validated it was smaller than total, invalidating the check and resulting in an unintended negative. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: David Rientjes <rientjes@google.com> Link: http://lkml.kernel.org/r/1337688268.9698.29.camel@twins Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
parent
74a5ce20e6
commit
b654f7de41
1 changed files with 11 additions and 4 deletions
|
@ -3503,15 +3503,22 @@ unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
|
|||
unsigned long scale_rt_power(int cpu)
|
||||
{
|
||||
struct rq *rq = cpu_rq(cpu);
|
||||
u64 total, available;
|
||||
u64 total, available, age_stamp, avg;
|
||||
|
||||
total = sched_avg_period() + (rq->clock - rq->age_stamp);
|
||||
/*
|
||||
* Since we're reading these variables without serialization make sure
|
||||
* we read them once before doing sanity checks on them.
|
||||
*/
|
||||
age_stamp = ACCESS_ONCE(rq->age_stamp);
|
||||
avg = ACCESS_ONCE(rq->rt_avg);
|
||||
|
||||
if (unlikely(total < rq->rt_avg)) {
|
||||
total = sched_avg_period() + (rq->clock - age_stamp);
|
||||
|
||||
if (unlikely(total < avg)) {
|
||||
/* Ensures that power won't end up being negative */
|
||||
available = 0;
|
||||
} else {
|
||||
available = total - rq->rt_avg;
|
||||
available = total - avg;
|
||||
}
|
||||
|
||||
if (unlikely((s64)total < SCHED_POWER_SCALE))
|
||||
|
|
Loading…
Add table
Reference in a new issue