linux-kernel - Re: [PATCH] mm: clarify usage of GFP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <746c1b7d-f082-8f15-e3ae-c1f09344789f@redhat.com>
Date:   Tue, 29 Sep 2020 15:29:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm: clarify usage of GFP_ATOMIC in !preemptible contexts

On 29.09.20 14:30, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> There is a general understanding that GFP_ATOMIC/GFP_NOWAIT are
> to be used from atomic contexts. E.g. from within a spin lock or from
> the IRQ context. This is correct but there are some atomic contexts
> where the above doesn't hold. One of them would be an NMI context.
> Page allocator has never supported that and the general fear of this
> context didn't let anybody to actually even try to use the allocator
> there. Good, but let's be more specific about that.
> 
> Another such a context, and that is where people seem to be more daring,
> is raw_spin_lock. Mostly because it simply resembles regular spin lock
> which is supported by the allocator and there is not any implementation
> difference with !RT kernels in the first place. Be explicit that such
> a context is not supported by the allocator. The underlying reason is
> that zone->lock would have to become raw_spin_lock as well and that has
> turned out to be a problem for RT
> (http://lkml.kernel.org/r/87mu305c1w.fsf@nanos.tec.linutronix.de).

Interesting

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb