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commit 14dbc56aa27d8b3f7cf99fa06e77fdc592b577c1
parent 9b00eb8ac2738b27a1469046f2ca76449dcdf04a
Author: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date:   Sat, 20 Oct 2018 15:03:45 +0200

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Ingo writes:
  "scheduler fixes:

   Two fixes: a CFS-throttling bug fix, and an interactivity fix."

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Fix the min_vruntime update logic in dequeue_entity()
  sched/fair: Fix throttle_list starvation with low CFS quota

Diffstat:
Mkernel/sched/fair.c | 24++++++++++++++++++++----
Mkernel/sched/sched.h | 2++
2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c @@ -4001,7 +4001,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) * put back on, and if we advance min_vruntime, we'll be placed back * further than we started -- ie. we'll be penalized. */ - if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE) + if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE) update_min_vruntime(cfs_rq); } @@ -4476,9 +4476,13 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq) /* * Add to the _head_ of the list, so that an already-started - * distribute_cfs_runtime will not see us + * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is + * not running add to the tail so that later runqueues don't get starved. */ - list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); + if (cfs_b->distribute_running) + list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); + else + list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); /* * If we're the first throttled task, make sure the bandwidth @@ -4622,14 +4626,16 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) * in us over-using our runtime if it is all used during this loop, but * only by limited amounts in that extreme case. */ - while (throttled && cfs_b->runtime > 0) { + while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) { runtime = cfs_b->runtime; + cfs_b->distribute_running = 1; raw_spin_unlock(&cfs_b->lock); /* we can't nest cfs_b->lock while distributing bandwidth */ runtime = distribute_cfs_runtime(cfs_b, runtime, runtime_expires); raw_spin_lock(&cfs_b->lock); + cfs_b->distribute_running = 0; throttled = !list_empty(&cfs_b->throttled_cfs_rq); cfs_b->runtime -= min(runtime, cfs_b->runtime); @@ -4740,6 +4746,11 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) /* confirm we're still not at a refresh boundary */ raw_spin_lock(&cfs_b->lock); + if (cfs_b->distribute_running) { + raw_spin_unlock(&cfs_b->lock); + return; + } + if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { raw_spin_unlock(&cfs_b->lock); return; @@ -4749,6 +4760,9 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) runtime = cfs_b->runtime; expires = cfs_b->runtime_expires; + if (runtime) + cfs_b->distribute_running = 1; + raw_spin_unlock(&cfs_b->lock); if (!runtime) @@ -4759,6 +4773,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) raw_spin_lock(&cfs_b->lock); if (expires == cfs_b->runtime_expires) cfs_b->runtime -= min(runtime, cfs_b->runtime); + cfs_b->distribute_running = 0; raw_spin_unlock(&cfs_b->lock); } @@ -4867,6 +4882,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) cfs_b->period_timer.function = sched_cfs_period_timer; hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); cfs_b->slack_timer.function = sched_cfs_slack_timer; + cfs_b->distribute_running = 0; } static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h @@ -346,6 +346,8 @@ struct cfs_bandwidth { int nr_periods; int nr_throttled; u64 throttled_time; + + bool distribute_running; #endif };