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Date:   Fri, 23 Aug 2019 14:22:42 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Daniel Vetter <daniel@ffwll.ch>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        Ingo Molnar <mingo@redhat.com>, Michal Hocko <mhocko@suse.com>,
        David Rientjes <rientjes@google.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Wei Wang <wvw@google.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jann Horn <jannh@google.com>, Feng Tang <feng.tang@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH 3/4] kernel.h: Add non_block_start/end()
Message-ID: <20190823122242.GN2349@hirez.programming.kicks-ass.net>
References: <20190820081902.24815-1-daniel.vetter@ffwll.ch>
 <20190820081902.24815-4-daniel.vetter@ffwll.ch>
 <20190820202440.GH11147@phenom.ffwll.local>
 <20190822161428.c9e4479207386d34745ea111@linux-foundation.org>
 <CAKMK7uGw_7uD=wH3bcR9xXSxAcAuYTLOZt3ue4TEvst1D0KzLQ@mail.gmail.com>
 <20190823121234.GB12968@ziepe.ca>
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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.