linux-kernel - Re: [PATCH v2 2/3] lockdep: Remove BROKEN flag of LOCKDEP

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Message-ID: <1508445681.2429.61.camel@wdc.com>
Date:   Thu, 19 Oct 2017 20:41:23 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "willy@...radead.org" <willy@...radead.org>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "byungchul.park@....com" <byungchul.park@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kernel-team@....com" <kernel-team@....com>
Subject: Re: [PATCH v2 2/3] lockdep: Remove BROKEN flag of
 LOCKDEP_CROSSRELEASE

On Thu, 2017-10-19 at 13:33 -0700, Matthew Wilcox wrote:
> For example, the page lock is not annotatable with lockdep -- we return
> to userspace with it held, for heaven's sake!  So it is quite easy for
> someone not familiar with the MM locking hierarchy to inadvertently
> introduce an ABBA deadlock against the page lock.  (ie me.  I did that.)
> Right now, that has to be caught by a human reviewer; if cross-release
> checking can catch that, then it's worth having.

Hello Matthew,

Although I agree that enabling lock inversion checking for page locks is
useful, I think my questions still apply to other locking objects than page
locks.

Thanks,

Bart.