linux-kernel - Re: [PATCH RFC] drivers/core: Replace lockdep_set_novalidate

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Message-ID: <Y+oDDXQW1mY1IA/+@hirez.programming.kicks-ass.net>
Date:   Mon, 13 Feb 2023 10:29:49 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Coly Li <colyli@...e.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        syzkaller <syzkaller@...glegroups.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH RFC] drivers/core: Replace lockdep_set_novalidate_class()
 with unique class keys

On Sun, Feb 12, 2023 at 03:51:05PM -0500, Kent Overstreet wrote:
> But, this would add a lot of complexity to lockdep, and this is the sort
> of situation where if you have a bug in the comparison function (i.e. it
> doesn't define a total ordering) it'll break things in terribly fun
> ways.

FWIW, it is possible to annotate an actual deadlock away with many of
the lockdep annotations -- care is always needed with this stuff.