linux-kernel - [PATCH] tracing: Don't assume possible cpu list have contenious number

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Message-Id: <20090310104437.A480.A69D9226@jp.fujitsu.com>
Date:	Tue, 10 Mar 2009 10:49:53 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>, Lai Jiangshan <laijs@...fujitsu.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	kosaki.motohiro@...fujitsu.com
Subject: [PATCH] tracing: Don't assume possible cpu list have contenious number 


"for (++cpu ; cpu < num_possible_cpus(); cpu++)" statement assume
possible cpus have contenious number. but that's wrong assumption.

Insted, cpumask_next() should be used.


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 kernel/trace/trace_workqueue.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
index e6c4d00..46b12db 100644
--- a/kernel/trace/trace_workqueue.c
+++ b/kernel/trace/trace_workqueue.c
@@ -91,7 +91,7 @@ static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
 	struct cpu_workqueue_stats *cws;
 	unsigned long flags;
 
-	WARN_ON(cpu < 0 || cpu >= num_possible_cpus());
+	WARN_ON(cpu < 0);
 
 	/* Workqueues are sometimes created in atomic context */
 	cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
@@ -175,12 +175,12 @@ static void *workqueue_stat_next(void *prev, int idx)
 	spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 	if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
 		spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
-		for (++cpu ; cpu < num_possible_cpus(); cpu++) {
-			ret = workqueue_stat_start_cpu(cpu);
-			if (ret)
-				return ret;
-		}
-		return NULL;
+		do {
+			cpu = cpumask_next(cpu, cpu_possible_mask);
+			if (cpu >= nr_cpu_ids)
+				return NULL;
+		} while (!(ret = workqueue_stat_start_cpu(cpu)));
+		return ret;
 	}
 	spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 
-- 
1.6.1.2



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