Hi Cong,
On 7/28/18 8:24 AM, Cong Wang wrote:
> Each time we sync cfs_rq->runtime_expires with cfs_b->runtime_expires,
> we should sync its ->expires_seq too. However it is missing
> for distribute_cfs_runtime(), especially the slack timer call path.
I don't think it's a problem, as expires_seq will get synced in
assign_cfs_rq_runtime().
Thanks,
Xunlei
>
> Fixes: 512ac999d275 ("sched/fair: Fix bandwidth timer clock drift condition")
> Cc: Xunlei Pang <xlp...@linux.alibaba.com>
> Cc: Ben Segall <bseg...@google.com>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
> ---
> kernel/sched/fair.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 2f0a0be4d344..910c50db3d74 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4857,7 +4857,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> }
>
> static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
> - u64 remaining, u64 expires)
> + u64 remaining, u64 expires, int expires_seq)
> {
> struct cfs_rq *cfs_rq;
> u64 runtime;
> @@ -4880,6 +4880,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth
> *cfs_b,
>
> cfs_rq->runtime_remaining += runtime;
> cfs_rq->runtime_expires = expires;
> + cfs_rq->expires_seq = expires_seq;
>
> /* we check whether we're throttled above */
> if (cfs_rq->runtime_remaining > 0)
> @@ -4905,7 +4906,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth
> *cfs_b,
> static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int
> overrun)
> {
> u64 runtime, runtime_expires;
> - int throttled;
> + int throttled, expires_seq;
>
> /* no need to continue the timer with no bandwidth constraint */
> if (cfs_b->quota == RUNTIME_INF)
> @@ -4933,6 +4934,7 @@ static int do_sched_cfs_period_timer(struct
> cfs_bandwidth *cfs_b, int overrun)
> cfs_b->nr_throttled += overrun;
>
> runtime_expires = cfs_b->runtime_expires;
> + expires_seq = cfs_b->expires_seq;
>
> /*
> * This check is repeated as we are holding onto the new bandwidth while
> @@ -4946,7 +4948,7 @@ static int do_sched_cfs_period_timer(struct
> cfs_bandwidth *cfs_b, int overrun)
> 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);
> + runtime_expires, expires_seq);
> raw_spin_lock(&cfs_b->lock);
>
> throttled = !list_empty(&cfs_b->throttled_cfs_rq);
> @@ -5055,6 +5057,7 @@ static __always_inline void
> return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
> static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
> {
> u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
> + int expires_seq;
> u64 expires;
>
> /* confirm we're still not at a refresh boundary */
> @@ -5068,12 +5071,13 @@ static void do_sched_cfs_slack_timer(struct
> cfs_bandwidth *cfs_b)
> runtime = cfs_b->runtime;
>
> expires = cfs_b->runtime_expires;
> + expires_seq = cfs_b->expires_seq;
> raw_spin_unlock(&cfs_b->lock);
>
> if (!runtime)
> return;
>
> - runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
> + runtime = distribute_cfs_runtime(cfs_b, runtime, expires, expires_seq);
>
> raw_spin_lock(&cfs_b->lock);
> if (expires == cfs_b->runtime_expires)
>
