sched/fair: Don't assign runtime for throttled cfs_rq
do_sched_cfs_period_timer() will refill cfs_b runtime and call distribute_cfs_runtime to unthrottle cfs_rq, sometimes cfs_b->runtime will allocate all quota to one cfs_rq incorrectly, then other cfs_rqs attached to this cfs_b can't get runtime and will be throttled. We find that one throttled cfs_rq has non-negative cfs_rq->runtime_remaining and cause an unexpetced cast from s64 to u64 in snippet: distribute_cfs_runtime() { runtime = -cfs_rq->runtime_remaining + 1; } The runtime here will change to a large number and consume all cfs_b->runtime in this cfs_b period. According to Ben Segall, the throttled cfs_rq can have account_cfs_rq_runtime called on it because it is throttled before idle_balance, and the idle_balance calls update_rq_clock to add time that is accounted to the task. This commit prevents cfs_rq to be assgined new runtime if it has been throttled until that distribute_cfs_runtime is called. Signed-off-by: Liangyan <liangyan.peng@linux.alibaba.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Ben Segall <bsegall@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: shanpeic@linux.alibaba.com Cc: stable@vger.kernel.org Cc: xlpang@linux.alibaba.com Fixes: d3d9dc330236 ("sched: Throttle entities exceeding their allowed bandwidth") Link: https://lkml.kernel.org/r/20190826121633.6538-1-liangyan.peng@linux.alibaba.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -4470,6 +4470,8 @@ static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
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if (likely(cfs_rq->runtime_remaining > 0))
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return;
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if (cfs_rq->throttled)
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return;
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/*
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* if we're unable to extend our runtime we resched so that the active
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* hierarchy can be throttled
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@ -4673,6 +4675,9 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
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if (!cfs_rq_throttled(cfs_rq))
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goto next;
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/* By the above check, this should never be true */
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SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
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runtime = -cfs_rq->runtime_remaining + 1;
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if (runtime > remaining)
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runtime = remaining;
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