linux-kernel - Re: [PATCH 3/4] kernel.h: Add non_block

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Message-ID: <20190823122242.GN2349@hirez.programming.kicks-ass.net>
Date:   Fri, 23 Aug 2019 14:22:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Ingo Molnar <mingo@...hat.com>, Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Christian König <christian.koenig@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Wei Wang <wvw@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jann Horn <jannh@...gle.com>, Feng Tang <feng.tang@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 3/4] kernel.h: Add non_block_start/end()

On Fri, Aug 23, 2019 at 09:12:34AM -0300, Jason Gunthorpe wrote:

> I still haven't heard a satisfactory answer why a whole new scheme is
> needed and a simple:
> 
>    if (IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP))
>         preempt_disable()
> 
> isn't sufficient to catch the problematic cases during debugging??
> IMHO the fact preempt is changed by the above when debugging is not
> material here. I think that information should be included in the
> commit message at least.

That has a much larger impact and actually changes behaviour, while the
relatively simple patch Daniel proposed only adds a warning but doesn't
affect behaviour.