From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH] mm: clarify usage of GFP_ATOMIC in !preemptible contexts
Date: Tue, 29 Sep 2020 15:29:59 +0200 [thread overview]
Message-ID: <746c1b7d-f082-8f15-e3ae-c1f09344789f@redhat.com> (raw)
In-Reply-To: <20200929123010.5137-1-mhocko@kernel.org>
On 29.09.20 14:30, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.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@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-09-29 13:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 12:30 [PATCH] mm: clarify usage of GFP_ATOMIC in !preemptible contexts Michal Hocko
2020-09-29 13:29 ` David Hildenbrand [this message]
2020-09-29 19:55 ` Thomas Gleixner
2020-09-29 20:33 ` Uladzislau Rezki
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