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From: Paul Turner <pjt@google.com>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>,
	Dan Carpenter <error27@gmail.com>
Subject: [patch 2/5] sched: (cleanup) remove redundant cfs_rq checks
Date: Fri, 21 Jan 2011 20:45:00 -0800	[thread overview]
Message-ID: <20110122044851.825284940@google.com> (raw)
In-Reply-To: 20110122044458.058531078@google.com

[-- Attachment #1: sched-remove_cfs_rq_checks.patch --]
[-- Type: text/plain, Size: 1252 bytes --]

Since updates are against an entity's queuing cfs_rq it's not possible to
enter update_cfs_{shares,load} with a NULL cfs_rq.  (Indeed, update_cfs_load
would crash prior to the check if we did anyway since we load is examined
during the initializers).  Also, in the update_cfs_load case there's no point
in maintaining averages for rq->cfs_rq since we don't perform shares
distribution at that level -- NULL check is replaced accordingly.

Thanks to Dan Carpenter for pointing out the deference before NULL check.

Signed-off-by: Paul Turner <pjt@google.com>

---
 kernel/sched_fair.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

Index: tip3/kernel/sched_fair.c
===================================================================
--- tip3.orig/kernel/sched_fair.c
+++ tip3/kernel/sched_fair.c
@@ -721,7 +721,7 @@ static void update_cfs_load(struct cfs_r
 	u64 now, delta;
 	unsigned long load = cfs_rq->load.weight;
 
-	if (!cfs_rq)
+	if (cfs_rq->tg == &root_task_group)
 		return;
 
 	now = rq_of(cfs_rq)->clock;
@@ -784,9 +784,6 @@ static void update_cfs_shares(struct cfs
 	struct sched_entity *se;
 	long load_weight, load, shares;
 
-	if (!cfs_rq)
-		return;
-
 	tg = cfs_rq->tg;
 	se = tg->se[cpu_of(rq_of(cfs_rq))];
 	if (!se)



  parent reply	other threads:[~2011-01-22  5:04 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-22  4:44 [patch 0/5] scheduler fixlets Paul Turner
2011-01-22  4:44 ` [patch 1/5] sched: fix sign under-flows in wake_affine Paul Turner
2011-01-26 12:09   ` [tip:sched/core] sched: Fix " tip-bot for Paul Turner
2011-01-22  4:45 ` Paul Turner [this message]
2011-01-26 12:10   ` [tip:sched/core] sched: Fix/remove redundant cfs_rq checks tip-bot for Paul Turner
2011-01-22  4:45 ` [patch 3/5] sched: simplify update_cfs_shares parameters Paul Turner
2011-01-26 12:11   ` [tip:sched/core] sched: Simplify " tip-bot for Paul Turner
2011-01-22  4:45 ` [patch 4/5] sched: use rq->clock_task instead of rq->clock for maintaining load averages Paul Turner
2011-01-26 12:10   ` [tip:sched/core] sched: Use rq->clock_task instead of rq->clock for correctly " tip-bot for Paul Turner
2011-01-22  4:45 ` [patch 5/5] sched: avoid expensive initial update_cfs_load() Paul Turner
2011-01-26 12:11   ` [tip:sched/core] sched: Avoid " tip-bot for Paul Turner
2011-01-26 12:36     ` Peter Zijlstra
2011-01-26 12:45   ` [tip:sched/core] sched: Avoid expensive initial update_cfs_load(), on UP too tip-bot for Peter Zijlstra
2011-01-27 11:58   ` tip-bot for Peter Zijlstra
2011-01-24 10:17 ` [patch 0/5] scheduler fixlets Peter Zijlstra

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