3.16.81-rc1 review patch. If anyone has any objections, please let me know.
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From: Ben Hutchings ben@decadent.org.uk
This reverts commit eb29ee5a3873134917a760bf9c416da0a089a0be, which was commit 512ac999d2755d2b7109e996a76b6fb8b888631d upstream. This introduced a regression and doesn't seem to have been suitable for older stable branches. (It has been fixed differently upstream.)
Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3163,7 +3163,6 @@ void __refill_cfs_bandwidth_runtime(stru now = sched_clock_cpu(smp_processor_id()); cfs_b->runtime = cfs_b->quota; cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); - cfs_b->expires_seq++; }
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) @@ -3186,7 +3185,6 @@ static int assign_cfs_rq_runtime(struct struct task_group *tg = cfs_rq->tg; struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); u64 amount = 0, min_amount, expires; - int expires_seq;
/* note: this is a positive sum as runtime_remaining <= 0 */ min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; @@ -3212,7 +3210,6 @@ static int assign_cfs_rq_runtime(struct cfs_b->idle = 0; } } - expires_seq = cfs_b->expires_seq; expires = cfs_b->runtime_expires; raw_spin_unlock(&cfs_b->lock);
@@ -3222,10 +3219,8 @@ static int assign_cfs_rq_runtime(struct * spread between our sched_clock and the one on which runtime was * issued. */ - if (cfs_rq->expires_seq != expires_seq) { - cfs_rq->expires_seq = expires_seq; + if ((s64)(expires - cfs_rq->runtime_expires) > 0) cfs_rq->runtime_expires = expires; - }
return cfs_rq->runtime_remaining > 0; } @@ -3251,9 +3246,12 @@ static void expire_cfs_rq_runtime(struct * has not truly expired. * * Fortunately we can check determine whether this the case by checking - * whether the global deadline(cfs_b->expires_seq) has advanced. + * whether the global deadline has advanced. It is valid to compare + * cfs_b->runtime_expires without any locks since we only care about + * exact equality, so a partial write will still work. */ - if (cfs_rq->expires_seq == cfs_b->expires_seq) { + + if (cfs_rq->runtime_expires != cfs_b->runtime_expires) { /* extend local deadline, drift is bounded above by 2 ticks */ cfs_rq->runtime_expires += TICK_NSEC; } else { --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -187,7 +187,6 @@ struct cfs_bandwidth { u64 quota, runtime; s64 hierarchal_quota; u64 runtime_expires; - int expires_seq;
int idle, timer_active; struct hrtimer period_timer, slack_timer; @@ -377,7 +376,6 @@ struct cfs_rq {
#ifdef CONFIG_CFS_BANDWIDTH int runtime_enabled; - int expires_seq; u64 runtime_expires; s64 runtime_remaining;