From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [btrfs/rt] lockdep false positive
Date: Mon, 23 Jan 2017 06:23:23 +0100 [thread overview]
Message-ID: <1485149003.4554.74.camel@gmail.com> (raw)
In-Reply-To: <1485107114.4467.73.camel@gmail.com>
On Sun, 2017-01-22 at 18:45 +0100, Mike Galbraith wrote:
> On Sun, 2017-01-22 at 09:46 +0100, Mike Galbraith wrote:
> > Greetings btrfs/lockdep wizards,
> >
> > RT trees have trouble with the BTRFS lockdep positive avoidance lock
> > class dance (see disk-io.c). Seems the trouble is due to RT not having
> > a means of telling lockdep that its rwlocks are recursive for read by
> > the lock owner only, combined with the BTRFS lock class dance assuming
> > that read_lock() is annotated rwlock_acquire_read(), which RT cannot
> > do, as that would be a big fat lie.
> >
> > Creating a rt_read_lock_shared() for btrfs_clear_lock_blocking_rw() did
> > indeed make lockdep happy as a clam for test purposes. (hm, submitting
> > that would be excellent way to replenish frozen shark supply:)
> >
> > Ideas?
>
> Hrm. The below seems to work fine, but /me strongly suspects that if
> it were this damn trivial, the issue would be long dead.
(iow, did I merely spell '2' as '3' vs creating the annotation I want)
next prev parent reply other threads:[~2017-01-23 5:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-22 8:46 [btrfs/rt] lockdep false positive Mike Galbraith
2017-01-22 17:45 ` Mike Galbraith
2017-01-22 18:25 ` Mike Galbraith
2017-01-23 5:23 ` Mike Galbraith [this message]
2017-01-23 9:07 ` Peter Zijlstra
2017-01-25 17:02 ` Sebastian Andrzej Siewior
2017-01-25 18:29 ` Mike Galbraith
2017-01-26 17:09 ` Sebastian Andrzej Siewior
2017-01-26 18:01 ` Mike Galbraith
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