linux-kernel - [PATCH v2 3/4] mm: kmemleak: Do not acquire scan_mutex in kmemleak_do

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Date:	Mon,  8 Jun 2015 15:29:17 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	vigneshr@...eaurora.org
Subject: [PATCH v2 3/4] mm: kmemleak: Do not acquire scan_mutex in kmemleak_do_cleanup()

The kmemleak_do_cleanup() work thread already waits for the
kmemleak_scan thread to finish via kthread_stop(). Waiting in
kthread_stop() while scan_mutex is held may lead to deadlock if
kmemleak_scan_thread() also waits to acquire for scan_mutex.

Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 mm/kmemleak.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index ecde522ff616..8a57e34625fa 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1762,7 +1762,6 @@ static void __kmemleak_do_cleanup(void)
  */
 static void kmemleak_do_cleanup(struct work_struct *work)
 {
-	mutex_lock(&scan_mutex);
 	stop_scan_thread();
 
 	/*
@@ -1777,7 +1776,6 @@ static void kmemleak_do_cleanup(struct work_struct *work)
 	else
 		pr_info("Kmemleak disabled without freeing internal data. "
 			"Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\"\n");
-	mutex_unlock(&scan_mutex);
 }
 
 static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
--
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