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From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-rt-users <linux-rt-users@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Clark Williams <williams@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	jack@suse.com
Subject: Re: [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current) with fsfreeze (4.19.25-rt16)
Date: Tue, 30 Apr 2019 16:29:50 +0200	[thread overview]
Message-ID: <20190430142950.GG2589@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190430141500.GE23020@redhat.com>

On Tue, Apr 30, 2019 at 04:15:01PM +0200, Oleg Nesterov wrote:
> Sorry, I don't understand...

So the problem is that on -RT rwsem uses PI mutexes, and the below just
cannot work.

Also see:

  https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/tree/include/linux/rwsem_rt.h?h=linux-5.0.y-rt
  https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/tree/kernel/locking/rwsem-rt.c?h=linux-5.0.y-rt

> On 04/30, Peter Zijlstra wrote:
> >
> > Thaw then does the reverse, frobs lockdep
> 
> Yes, in particular it does
> 
> 	lockdep_sb_freeze_acquire()
> 		percpu_rwsem_acquire()
> 			sem->rw_sem.owner = current;
> 

Oh ARGGH, I missed that. This is horrible :-(


  reply	other threads:[~2019-04-30 14:30 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-26  9:34 [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current) with fsfreeze (4.19.25-rt16) Juri Lelli
2019-03-28 10:17 ` Sebastian Andrzej Siewior
2019-04-19  8:56 ` Juri Lelli
2019-04-30 12:51   ` Sebastian Andrzej Siewior
2019-04-30 13:28     ` Peter Zijlstra
2019-04-30 13:45       ` Sebastian Andrzej Siewior
2019-04-30 14:01         ` Peter Zijlstra
2019-04-30 14:15       ` Oleg Nesterov
2019-04-30 14:29         ` Peter Zijlstra [this message]
2019-04-30 14:42         ` Oleg Nesterov
2019-04-30 14:44           ` Peter Zijlstra
2019-04-30 14:53             ` Oleg Nesterov
2019-05-01 17:09       ` Peter Zijlstra
2019-05-01 17:26         ` Waiman Long
2019-05-01 18:54           ` Peter Zijlstra
2019-05-01 19:22             ` Davidlohr Bueso
2019-05-01 19:25               ` Peter Zijlstra
2019-05-02 10:09         ` Oleg Nesterov
2019-05-02 11:42           ` Oleg Nesterov
2019-05-03 14:50             ` Peter Zijlstra
2019-05-03 15:25               ` Peter Zijlstra
2019-05-06 16:50               ` Oleg Nesterov
2019-06-19  9:50                 ` Peter Zijlstra
2019-05-03 14:16           ` Peter Zijlstra
2019-05-03 15:37             ` Oleg Nesterov
2019-05-03 15:46               ` Peter Zijlstra

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