sched: add rq_clock()/__rq_clock()
add rq_clock()/__rq_clock(), a robust wrapper around sched_clock(), used by CFS. It protects against common type of sched_clock() problems (caused by hardware): time warps forwards and backwards. Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -388,6 +388,52 @@ static inline int cpu_of(struct rq *rq)
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#endif
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}
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/*
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* Per-runqueue clock, as finegrained as the platform can give us:
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*/
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static unsigned long long __rq_clock(struct rq *rq)
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{
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u64 prev_raw = rq->prev_clock_raw;
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u64 now = sched_clock();
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s64 delta = now - prev_raw;
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u64 clock = rq->clock;
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/*
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* Protect against sched_clock() occasionally going backwards:
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*/
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if (unlikely(delta < 0)) {
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clock++;
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rq->clock_warps++;
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} else {
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/*
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* Catch too large forward jumps too:
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*/
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if (unlikely(delta > 2*TICK_NSEC)) {
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clock++;
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rq->clock_overflows++;
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} else {
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if (unlikely(delta > rq->clock_max_delta))
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rq->clock_max_delta = delta;
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clock += delta;
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}
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}
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rq->prev_clock_raw = now;
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rq->clock = clock;
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return clock;
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}
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static inline unsigned long long rq_clock(struct rq *rq)
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{
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int this_cpu = smp_processor_id();
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if (this_cpu == cpu_of(rq))
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return __rq_clock(rq);
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return rq->clock;
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}
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/*
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* The domain tree (rq->sd) is protected by RCU's quiescent state transition.
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* See detach_destroy_domains: synchronize_sched for details.
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