linux-kernel - [tip:sched/core] sched: Fix/remove redundant cfs

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Date:	Wed, 26 Jan 2011 12:10:13 GMT
From:	tip-bot for Paul Turner <pjt@...gle.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, pjt@...gle.com, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:sched/core] sched: Fix/remove redundant cfs_rq checks

Commit-ID:  b815f1963e47b9b69bb17e0588bd5af5b1114ae0
Gitweb:     http://git.kernel.org/tip/b815f1963e47b9b69bb17e0588bd5af5b1114ae0
Author:     Paul Turner <pjt@...gle.com>
AuthorDate: Fri, 21 Jan 2011 20:45:00 -0800
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 26 Jan 2011 12:31:02 +0100

sched: Fix/remove redundant cfs_rq checks

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@...gle.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <20110122044851.825284940@...gle.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched_fair.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ccecfec..1997383 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -722,7 +722,7 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
 	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;
@@ -830,9 +830,6 @@ static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
 	struct sched_entity *se;
 	long shares;
 
-	if (!cfs_rq)
-		return;
-
 	tg = cfs_rq->tg;
 	se = tg->se[cpu_of(rq_of(cfs_rq))];
 	if (!se)
--
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