linux-kernel - Re: [PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in __lock

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Message-ID: <20190929144912.GA2011833@kroah.com>
Date:   Sun, 29 Sep 2019 16:49:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        syzbot+53383ae265fb161ef488@...kaller.appspotmail.com,
        Waiman Long <longman@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in
 __lock_downgrade()

On Sun, Sep 29, 2019 at 11:43:38PM +0900, Tetsuo Handa wrote:
> On 2019/09/29 22:54, Greg Kroah-Hartman wrote:
> > From: Waiman Long <longman@...hat.com>
> > 
> > [ Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf ]
> > 
> > Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
> > warning right after a previous lockdep warning. It is likely that the
> > previous warning turned off lock debugging causing the lockdep to have
> > inconsistency states leading to the lock downgrade warning.
> > 
> > Fix that by add a check for debug_locks at the beginning of
> > __lock_downgrade().
> 
> Please drop "[PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in __lock_downgrade()".
> We had a revert patch shown below in the past.

Ugh, I missed that, thanks.

> "[PATCH 4.19 37/63] locking/lockdep: Add debug_locks check in __lock_downgrade() - again" seems the correct patch.

Ok, will keep that one.  And will drop the "again" part of that subject
line, had to add that to make quilt happy :(

thanks for the review.

greg k-h