linux-kernel - Re: [PATCH] kthread: finer-grained lockdep/cross-release completion

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Message-ID: <20171207122255.zi5ishny24k66ik7@hirez.programming.kicks-ass.net>
Date:   Thu, 7 Dec 2017 13:22:56 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Marta Lofstedt <marta.lofstedt@...el.com>,
        Byungchul Park <byungchul.park@....com>,
        Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>, Shaohua Li <shli@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Oleg Nesterov <oleg@...hat.com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH] kthread: finer-grained lockdep/cross-release completion

On Thu, Dec 07, 2017 at 11:08:49AM +0100, Daniel Vetter wrote:
> Since -rc1 we're hitting a bunch of lockdep splats using the new
> cross-release stuff around the 2 kthread completions. In all cases
> they are because totally independent uses of kthread are mixed up by
> lockdep into the same locking class, creating artificial deadlocks.
> 
> Fix this by converting kthread code in the same way as e.g.
> alloc_workqueue already works: Use macros for the public api so we can
> have a callsite specific lockdep key, then pass that through the
> entire callchain. Due to the many entry points this is slightly
> tedious.

Do you have a splat somewhere? I'm having trouble seeing how all this
comes together. That is, I've no real idea what you're actual problem is
and if this is the right solution.