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

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Date:   Thu, 15 Mar 2018 11:31:57 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Byungchul Park <byungchul.park@....com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        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>, kernel-team@....com,
        Amir Goldstein <amir73il@...il.com>,
        "Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH] kthread: finer-grained lockdep/cross-release completion

On Wed, Dec 20, 2017 at 2:14 AM, Byungchul Park <byungchul.park@....com> wrote:
> On 12/19/2017 6:59 PM, Daniel Vetter wrote:
>>
>> On Mon, Dec 18, 2017 at 09:42:13AM -0800, Linus Torvalds wrote:
>>>
>>> On Sun, Dec 17, 2017 at 11:11 PM, Daniel Vetter <daniel@...ll.ch> wrote:
>>>>
>>>>
>>>> This didn't seem to have made it into -rc4. Anything needed to get it
>>>> going?
>>>
>>>
>>> Do you actually see the problem in -rc4?
>>>
>>> Because we ended up removing the cross-release checking due to other
>>> developers complaining. It seemed to need a lot more work before it
>>> was ready.
>>>
>>> So I suspect the patch is simply not relevant any more (even if it's
>>> not necessarily wrong either).
>>
>>
>> Awww ... I like the cross release stuff, it's catching lots of good bugs
>> for us - writing a gpu memory manager that's supposed to interface with
>> the core one ain't the simplest thing to get right. That's also why we're
>> going around and fixing up fallout (we've worked on the worker annotations
>> for 4.14 too). I guess next release, hopefully.
>>
>> I think between 4.14 and 4.15 attemps cross-release spotted around 5 or so
>> genuine deadlocks in i915 code. And at least right now, with the current
>> set of fixups our CI runs are splat-free. So at least a Kconfig option
>> would be nice, to be able to enable it easily when you want to.
>>
>> Wrt us not noticing: Getting the patches in through normal means takes too
>> long, so we constantly carry arounda  bunch of fixup patches to address
>> serious issues that block CI (no lockdep is no good CI). That's why we
>> won't immediately notice when an issue is resolved some other way.
>
>
> Hello Ingo and Linus,
>
> IMO, taking it off by default is enough. What fs folk actually
> wanted is not to remove whole stuff but make it off by default.
>
> Cross-release logic itself makes sense. Please consider it back
> and apply my patch making it off by default.
>
> I will do what I can do for the classification in layered fs.

Is there any progress on getting cross-release enabled again?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch