sched: Make scale_rt_power() deal with backward clocks
Mike reported that, while unlikely, its entirely possible for scale_rt_power() to see the time go backwards. This yields rather 'interesting' results. So like all other sites that deal with clocks; make this one ignore backward clock movement too. Reported-by: Mike Galbraith <bitbucket@online.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140227094035.GZ9987@twins.programming.kicks-ass.net Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -5564,6 +5564,7 @@ static unsigned long scale_rt_power(int cpu)
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{
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{
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struct rq *rq = cpu_rq(cpu);
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struct rq *rq = cpu_rq(cpu);
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u64 total, available, age_stamp, avg;
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u64 total, available, age_stamp, avg;
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s64 delta;
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/*
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/*
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* Since we're reading these variables without serialization make sure
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* Since we're reading these variables without serialization make sure
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@ -5572,7 +5573,11 @@ static unsigned long scale_rt_power(int cpu)
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age_stamp = ACCESS_ONCE(rq->age_stamp);
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age_stamp = ACCESS_ONCE(rq->age_stamp);
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avg = ACCESS_ONCE(rq->rt_avg);
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avg = ACCESS_ONCE(rq->rt_avg);
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total = sched_avg_period() + (rq_clock(rq) - age_stamp);
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delta = rq_clock(rq) - age_stamp;
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if (unlikely(delta < 0))
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delta = 0;
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total = sched_avg_period() + delta;
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if (unlikely(total < avg)) {
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if (unlikely(total < avg)) {
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/* Ensures that power won't end up being negative */
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/* Ensures that power won't end up being negative */
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