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

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Message-ID: <20190521144713.GX32329@dhcp22.suse.cz>
Date:   Tue, 21 May 2019 16:47:13 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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] kernel.h: Add non_block_start/end()

On Tue 21-05-19 14:43:38, Cristopher Lameter wrote:
> On Tue, 21 May 2019, Daniel Vetter wrote:
> 
> > In some special cases we must not block, but there's not a
> > spinlock, preempt-off, irqs-off or similar critical section already
> > that arms the might_sleep() debug checks. Add a non_block_start/end()
> > pair to annotate these.
> 
> Just putting preempt on/off around these is not sufficient?

It is not a critical section. It is a _debugging_ facility to help
discover blocking contexts.
-- 
Michal Hocko
SUSE Labs