linux-kernel - Re: [PATCH] sched: fix unlocked reads of some cfs

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Message-ID: <20140522153504.GY30445@twins.programming.kicks-ass.net>
Date:	Thu, 22 May 2014 17:35:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ben Segall <bsegall@...gle.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Roman Gushchin <klamm@...dex-team.ru>, pjt@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: fix unlocked reads of some cfs_b->quota/period

On Mon, May 19, 2014 at 03:49:45PM -0700, Ben Segall wrote:
> @@ -3783,7 +3787,7 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
>  		 * clock_task is not advancing so we just need to make sure
>  		 * there's some valid quota amount
>  		 */
> -		cfs_rq->runtime_remaining = cfs_b->quota;
> +		cfs_rq->runtime_remaining = 1;
>  		if (cfs_rq_throttled(cfs_rq))
>  			unthrottle_cfs_rq(cfs_rq);
>  	}
> 

That ^, causes:

kernel/sched/fair.c: In function ‘unthrottle_offline_cfs_rqs’:
kernel/sched/fair.c:3782:25: warning: unused variable ‘cfs_b’ [-Wunused-variable]

Stuck this on:

---
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3779,8 +3779,6 @@ static void __maybe_unused unthrottle_of
 	struct cfs_rq *cfs_rq;
 
 	for_each_leaf_cfs_rq(rq, cfs_rq) {
-		struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
-
 		if (!cfs_rq->runtime_enabled)
 			continue;
 

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