From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: paulmck@linux.vnet.ibm.com
Cc: tglx@linutronix.de, laijs@cn.fujitsu.com, darren@dvhart.com,
rostedt@goodmis.org, mingo@elte.hu, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with irqs disabled
Date: Thu, 21 Jul 2011 13:32:48 +0200 [thread overview]
Message-ID: <1311247968.29152.122.camel@twins> (raw)
In-Reply-To: <20110719201410.GA10553@linux.vnet.ibm.com>
On Tue, 2011-07-19 at 13:14 -0700, Paul E. McKenney wrote:
> Because rcu_read_unlock() can be invoked with interrupts disabled, it can
> in turn invoke rt_mutex_unlock() with interrupts disabled. This situation
> results in lockdep splats (https://lkml.org/lkml/2011/7/7/362) because the
> rt_mutex structure's ->lock_wait is acquired elsewhere without disabling
> interrupts, which can result in deadlocks.
>
> This commit therefore changes the rt_mutex structure's ->lock_wait
> acquisitions to disable interrupts.
>
> An alternative fix is to prohibit invoking rcu_read_unlock() with
> interrupts disabled unless the entire preceding RCU read-side critical
> section has run with interrupts disabled. However, there is already
> at least one case in mainline where this potential rule is violated,
> and there might well be many more. These would likely be found one at
> a time using the lockdep-water-torture method, hence the alternative
> fix in the form of this commit.
Thomas, I'm inclined to merge this, any objections?
next prev parent reply other threads:[~2011-07-21 11:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-19 20:14 [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with irqs disabled Paul E. McKenney
2011-07-21 11:32 ` Peter Zijlstra [this message]
2011-07-23 22:03 ` Paul E. McKenney
2011-07-23 23:20 ` Thomas Gleixner
2011-07-24 0:05 ` Thomas Gleixner
2011-07-24 5:17 ` Paul E. McKenney
2011-07-24 9:00 ` Thomas Gleixner
2011-07-24 15:56 ` Paul E. McKenney
2011-08-20 1:31 ` Arnaud Lacombe
2011-08-20 17:09 ` Paul E. McKenney
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