linux-kernel - [PATCH] softlockup: convert read_lock in hung_task to rcu_read

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Message-ID: <20090205175608.GA10819@google.com>
Date:	Thu, 5 Feb 2009 09:56:08 -0800
From:	Mandeep Singh Baines <msb@...gle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, rientjes@...gle.com,
	mbligh@...gle.com, thockin@...gle.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] softlockup: convert read_lock in hung_task to rcu_read_lock

Ingo Molnar (mingo@...e.hu) wrote:
> 
> I've applied your patch to tip:core/softlockup, thanks Mandeep!
> 

Oops, I put the conversion to rcu_read_lock in a seperate patch. I
understand now the convention is to use a patch series only when the
patches can be applied independently.

---
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@...llo.nl>
Signed-off-by: Mandeep Singh Baines <msb@...gle.com>
---
 kernel/hung_task.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index d32d293..34b678c 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)
-- 
1.5.4.5

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