linux-kernel - Re: [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current) with fsfreeze (4.19.25-rt16)

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Message-ID: <20190430144252.GF23020@redhat.com>
Date:   Tue, 30 Apr 2019 16:42:53 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Clark Williams <williams@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>, jack@...e.com
Subject: Re: [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) !=
 current) with fsfreeze (4.19.25-rt16)

I have cloned linux-rt-devel.git

If I understand correctly, in rt rw_semaphore is actually defined in rwsem_rt.h
so percpu_rwsem_acquire() should probably do

	sem->rw_sem.rtmutex.owner = current;

?


On 04/30, Oleg Nesterov wrote:
>
> Sorry, I don't understand...
> 
> 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;
> 
> 	
> > and then does: percpu_up_write().
> >
> > percpu_up_write() on up_write(). And note how __up_write() has:
> >
> > 	DEBUG_RWSEMS_WARN_ON(sem->owner != current, sem);
> 
> and everything looks correct, sem->owner == current by the time
> thaw_super_locked() does percpu_up_write/up_write.
> 
> Oleg.