lkml.org 
[lkml]   [2020]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 3.16 58/63] Revert "sched/fair: Fix bandwidth timer clock drift condition"
3.16.81-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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;

\
 
 \ /
  Last update: 2020-01-08 20:48    [W:0.258 / U:0.972 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site