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From: tip-bot for Paul Turner <pjt@google.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com,
	a.p.zijlstra@chello.nl, pjt@google.com, tglx@linutronix.de,
	mingo@elte.hu
Subject: [tip:sched/core] sched: Fix/remove redundant cfs_rq checks
Date: Wed, 26 Jan 2011 12:10:13 GMT	[thread overview]
Message-ID: <tip-b815f1963e47b9b69bb17e0588bd5af5b1114ae0@git.kernel.org> (raw)
In-Reply-To: <20110122044851.825284940@google.com>

Commit-ID:  b815f1963e47b9b69bb17e0588bd5af5b1114ae0
Gitweb:     http://git.kernel.org/tip/b815f1963e47b9b69bb17e0588bd5af5b1114ae0
Author:     Paul Turner <pjt@google.com>
AuthorDate: Fri, 21 Jan 2011 20:45:00 -0800
Committer:  Ingo Molnar <mingo@elte.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@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110122044851.825284940@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.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)

  reply	other threads:[~2011-01-26 12:10 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 ` [patch 2/5] sched: (cleanup) remove redundant cfs_rq checks Paul Turner
2011-01-26 12:10   ` tip-bot for Paul Turner [this message]
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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