[PATCH RT 04/12] rtmutex: Handle non enqueued waiters gracefully

Path	csiph.com!news.mixmin.net!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Steven Rostedt <rostedt@goodmis.org>
Newsgroups	linux.kernel
Subject	[PATCH RT 04/12] rtmutex: Handle non enqueued waiters gracefully
Date	Fri, 26 Feb 2016 22:40:04 +0100
Message-ID	<r6yhe-RJ-49@gated-at.bofh.it> (permalink)
References	<r6yhc-RJ-15@gated-at.bofh.it>
X-Original-To	linux-kernel@vger.kernel.org, linux-rt-users <linux-rt-users@vger.kernel.org>
User-Agent	quilt/0.61-1
MIME-Version	1.0
Content-Type	text/plain; charset=ISO-8859-15
Content-Disposition	inline; filename=0004-rtmutex-Handle-non-enqueued-waiters-gracefully.patch
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	39
Organization	linux.* mail to news gateway
X-Original-Cc	Thomas Gleixner <tglx@linutronix.de>, Carsten Emde <C.Emde@osadl.org>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, John Kacur <jkacur@redhat.com>, Paul Gortmaker <paul.gortmaker@windriver.com>, <stable-rt@vger.kernel.org>
X-Original-Date	Fri, 26 Feb 2016 16:32:39 -0500
X-Original-Message-ID	<20160226213340.609345335@goodmis.org>
X-Original-References	<20160226213235.253312067@goodmis.org>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1344711

Show key headers only | View raw

3.18.27-rt26-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

Yimin debugged that in case of a PI wakeup in progress when
rt_mutex_start_proxy_lock() calls task_blocks_on_rt_mutex() the latter
returns -EAGAIN and in consequence the remove_waiter() call runs into
a BUG_ON() because there is nothing to remove.

Guard it with rt_mutex_has_waiters(). This is a quick fix which is
easy to backport. The proper fix is to have a central check in
remove_waiter() so we can call it unconditionally.

Reported-and-debugged-by: Yimin Deng <yimin11.deng@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/locking/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 64973df0c686..c1b7d5b1be7e 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -2144,7 +2144,7 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
 		ret = 0;
 	}
 
-	if (unlikely(ret))
+	if (ret && rt_mutex_has_waiters(lock))
 		remove_waiter(lock, waiter);
 
 	raw_spin_unlock(&lock->wait_lock);
-- 
2.7.0

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH RT 04/12] rtmutex: Handle non enqueued waiters gracefully Steven Rostedt <rostedt@goodmis.org> - 2016-02-26 22:40 +0100

csiph-web