Date:   Tue, 14 Feb 2023 15:16:54 -0500
From:   Kent Overstreet <kent.overstreet@linux.dev>
To:     Peter Zijlstra <peterz@infradead.org>
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 Tue, Feb 14, 2023 at 12:05:27PM +0100, Peter Zijlstra wrote:
> This is lock order per decree, if you get the order function wrong
> lockdep will not see the inversion but you *will* deadlock.

Yeah, that's what I mean. Given that a subclass isn't a fixed thing you
assign to a lock, just something you magic up as needed - I just don't
see what this gets us?

Why not just tell lockdep what the order function is directly?

(I know, I've been saying I'd write a patch for this, I'll get around to
it, I swear :)