linux-kernel - [PATCH] Fix optimized search

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Message-ID: <20071121030838.16020.59975.stgit@novell1.haskins.net>
Date:	Tue, 20 Nov 2007 22:10:10 -0500
From:	Gregory Haskins <ghaskins@...ell.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>
Cc:	Christoph Lameter <clameter@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Gregory Haskins <ghaskins@...ell.com>
Subject: [PATCH] Fix optimized search

I spied a few more issues from http://lkml.org/lkml/2007/11/20/590.

Patch is below..

Regards,
-Greg

-----------------

Include cpu 0 in the search, and eliminate the redundant cpu_set since
the bit should already be set in the mask.

Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
---

 kernel/sched_rt.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 28feeff..fbf4fb1 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -297,7 +297,7 @@ static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
 static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 {
 	int       lowest_prio = -1;
-	int       lowest_cpu  = 0;
+	int       lowest_cpu  = -1;
 	int       count       = 0;
 	int       cpu;
 
@@ -319,7 +319,7 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 			 * and the count==1 will cause the algorithm
 			 * to use the first bit found.
 			 */
-			if (lowest_cpu) {
+			if (lowest_cpu != -1) {
 				cpus_clear(*lowest_mask);
 				cpu_set(rq->cpu, *lowest_mask);
 			}
@@ -335,7 +335,6 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 				lowest_cpu = cpu;
 				count = 0;
 			}
-			cpu_set(rq->cpu, *lowest_mask);
 			count++;
 		} else
 			cpu_clear(cpu, *lowest_mask);
@@ -346,7 +345,7 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 	 * runqueues that were of higher prio than
 	 * the lowest_prio.
 	 */
-	if (lowest_cpu) {
+	if (lowest_cpu != -1) {
 		/*
 		 * Perhaps we could add another cpumask op to
 		 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);

-
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