linux-kernel - [PATCH 4/4] kmemleak: Slightly change the policy on newly allocated objects

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Message-ID: <20090626141258.31504.36983.stgit@pc1117.cambridge.arm.com>
Date:	Fri, 26 Jun 2009 15:12:58 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	linux-kernel@...r.kernel.org
Cc:	Dave Jones <davej@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Sergey Senozhatsky <sergey.senozhatsky@...l.by>
Subject: [PATCH 4/4] kmemleak: Slightly change the policy on newly allocated
	objects

Newly allocated objects are more likely to be reported as false
positives. Kmemleak ignores the reporting of objects younger than 5
seconds. However, this age was calculated after the memory scanning
completed which usually takes longer than 5 seconds. This patch
make the minimum object age calculation in relation to the start of the
memory scanning.

Signed-off-by: Catalin Marinas <catalin.marinas@....com>
---
 mm/kmemleak.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index e96e0ec..c37e8e5 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -190,7 +190,9 @@ static unsigned long max_addr;
 static unsigned long next_scan_yield;
 static struct task_struct *scan_thread;
 static unsigned long jiffies_scan_yield;
+/* used to avoid reporting of recently allocated objects */
 static unsigned long jiffies_min_age;
+static unsigned long jiffies_last_scan;
 /* delay between automatic memory scannings */
 static signed long jiffies_scan_wait;
 /* enables or disables the task stacks scanning */
@@ -284,7 +286,8 @@ static int color_gray(const struct kmemleak_object *object)
 static int unreferenced_object(struct kmemleak_object *object)
 {
 	return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
-		time_is_before_eq_jiffies(object->jiffies + jiffies_min_age);
+		time_before_eq(object->jiffies + jiffies_min_age,
+			       jiffies_last_scan);
 }
 
 /*
@@ -927,6 +930,8 @@ static void kmemleak_scan(void)
 	int i;
 	int new_leaks = 0;
 
+	jiffies_last_scan = jiffies;
+
 	/* prepare the kmemleak_object's */
 	rcu_read_lock();
 	list_for_each_entry_rcu(object, &object_list, object_list) {

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