From 94be52dc075a32af4aa73d7e10f68734d62d6af2 Mon Sep 17 00:00:00 2001
From: Mandeep Singh Baines <msb@google.com>
Date: Thu, 5 Feb 2009 09:56:08 -0800
Subject: [PATCH] softlockup: convert read_lock in hung_task to rcu_read_lock

Since the tasklist is protected by rcu list operations, it is safe
to convert the read_lock()s to rcu_read_lock().

Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Mandeep Singh Baines <msb@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/hung_task.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 481ca8b5c2bc..3951a80e7cbe 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -155,7 +155,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 	if (test_taint(TAINT_DIE) || did_panic)
 		return;
 
-	read_lock(&tasklist_lock);
+	rcu_read_lock();
 	do_each_thread(g, t) {
 		if (!--max_count)
 			goto unlock;
@@ -171,7 +171,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 			check_hung_task(t, now, timeout);
 	} while_each_thread(g, t);
  unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 }
 
 static void update_poll_jiffies(void)
-- 
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