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SubjectRe: [PATCH -next v2] sched/fair: fix -Wunused-but-set-variable warnings
On Tue, Sep 03, 2019 at 09:03:26AM -0400, Qian Cai wrote:
> Ingo or Peter, please take a look at this trivial patch. Still see the warning
> in linux-next every day.
>
> On Tue, 2019-08-20 at 14:40 -0400, Qian Cai wrote:
> > The linux-next commit "sched/fair: Fix low cpu usage with high
> > throttling by removing expiration of cpu-local slices" [1] introduced a
> > few compilation warnings,
> >
> > kernel/sched/fair.c: In function '__refill_cfs_bandwidth_runtime':
> > kernel/sched/fair.c:4365:6: warning: variable 'now' set but not used
> > [-Wunused-but-set-variable]
> > kernel/sched/fair.c: In function 'start_cfs_bandwidth':
> > kernel/sched/fair.c:4992:6: warning: variable 'overrun' set but not used
> > [-Wunused-but-set-variable]
> >
> > Also, __refill_cfs_bandwidth_runtime() does no longer update the
> > expiration time, so fix the comments accordingly.
> >
> > [1] https://lore.kernel.org/lkml/1558121424-2914-1-git-send-email-chiluk+linux
> > @indeed.com/
> >
> > Signed-off-by: Qian Cai <cai@lca.pw>

Rewrote the Changelog like so:

---
Subject: sched/fair: Fix -Wunused-but-set-variable warnings
From: Qian Cai <cai@lca.pw>
Date: Tue, 20 Aug 2019 14:40:55 -0400

Commit de53fd7aedb1 ("sched/fair: Fix low cpu usage with high
throttling by removing expiration of cpu-local slices") introduced a
few compilation warnings:

kernel/sched/fair.c: In function '__refill_cfs_bandwidth_runtime':
kernel/sched/fair.c:4365:6: warning: variable 'now' set but not used [-Wunused-but-set-variable]
kernel/sched/fair.c: In function 'start_cfs_bandwidth':
kernel/sched/fair.c:4992:6: warning: variable 'overrun' set but not used [-Wunused-but-set-variable]

Also, __refill_cfs_bandwidth_runtime() does no longer update the
expiration time, so fix the comments accordingly.

Fixes: de53fd7aedb1 ("sched/fair: Fix low cpu usage with high throttling by removing expiration of cpu-local slices")
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Reviewed-by: Dave Chiluk <chiluk+linux@indeed.com>
Cc: mingo@redhat.com
Cc: pauld@redhat.com
Link: https://lkml.kernel.org/r/1566326455-8038-1-git-send-email-cai@lca.pw
---
kernel/sched/fair.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4386,21 +4386,16 @@ static inline u64 sched_cfs_bandwidth_sl
}

/*
- * Replenish runtime according to assigned quota and update expiration time.
- * We use sched_clock_cpu directly instead of rq->clock to avoid adding
- * additional synchronization around rq->lock.
+ * Replenish runtime according to assigned quota. We use sched_clock_cpu
+ * directly instead of rq->clock to avoid adding additional synchronization
+ * around rq->lock.
*
* requires cfs_b->lock
*/
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
- u64 now;
-
- if (cfs_b->quota == RUNTIME_INF)
- return;
-
- now = sched_clock_cpu(smp_processor_id());
- cfs_b->runtime = cfs_b->quota;
+ if (cfs_b->quota != RUNTIME_INF)
+ cfs_b->runtime = cfs_b->quota;
}

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
@@ -5021,15 +5016,13 @@ static void init_cfs_rq_runtime(struct c

void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
- u64 overrun;
-
lockdep_assert_held(&cfs_b->lock);

if (cfs_b->period_active)
return;

cfs_b->period_active = 1;
- overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
+ hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
}

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