sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup

[thirdparty/linux.git] / kernel / sched / fair.c

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 40bd1e27b1b79f88e3ba23b413e5d0d7f1b28094..a4d9e14bf13891482bb717d03946699fa04958b1 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4885,6 +4885,8 @@ static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
        return HRTIMER_NORESTART;
 }
 
+extern const u64 max_cfs_quota_period;
+
 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
 {
        struct cfs_bandwidth *cfs_b =
@@ -4892,6 +4894,7 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
        unsigned long flags;
        int overrun;
        int idle = 0;
+       int count = 0;
 
        raw_spin_lock_irqsave(&cfs_b->lock, flags);
        for (;;) {
@@ -4899,6 +4902,28 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
                if (!overrun)
                        break;
 
+               if (++count > 3) {
+                       u64 new, old = ktime_to_ns(cfs_b->period);
+
+                       new = (old * 147) / 128; /* ~115% */
+                       new = min(new, max_cfs_quota_period);
+
+                       cfs_b->period = ns_to_ktime(new);
+
+                       /* since max is 1s, this is limited to 1e9^2, which fits in u64 */
+                       cfs_b->quota *= new;
+                       cfs_b->quota = div64_u64(cfs_b->quota, old);
+
+                       pr_warn_ratelimited(
+       "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us %lld, cfs_quota_us = %lld)\n",
+                               smp_processor_id(),
+                               div_u64(new, NSEC_PER_USEC),
+                               div_u64(cfs_b->quota, NSEC_PER_USEC));
+
+                       /* reset count so we don't come right back in here */
+                       count = 0;
+               }
+
                idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
        }
        if (idle)