Date:   Mon, 13 Feb 2023 10:29:49 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kent Overstreet <kent.overstreet@linux.dev>
Cc:     Alan Stern <stern@rowland.harvard.edu>,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Coly Li <colyli@suse.de>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        syzkaller <syzkaller@googlegroups.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        Hillf Danton <hdanton@sina.com>
Subject: Re: [PATCH RFC] drivers/core: Replace lockdep_set_novalidate_class()
 with unique class keys
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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.