From: Oscar Salvador <osalvador@suse.de>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>,
Alexander Duyck <alexanderduyck@fb.com>,
Minchan Kim <minchan@kernel.org>, Michal Hocko <mhocko@suse.com>,
David Hildenbrand <david@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 resend] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove
Date: Wed, 14 Apr 2021 09:18:02 +0200 [thread overview]
Message-ID: <20210414071756.GA20401@linux> (raw)
In-Reply-To: <20210412120842.GY3697@techsingularity.net>
On Mon, Apr 12, 2021 at 01:08:42PM +0100, Mel Gorman wrote:
> zone_pcp_reset allegedly protects against a race with drain_pages
> using local_irq_save but this is bogus. local_irq_save only operates
> on the local CPU. If memory hotplug is running on CPU A and drain_pages
> is running on CPU B, disabling IRQs on CPU A does not affect CPU B and
> offers no protection.
>
> This patch deletes IRQ disable/enable on the grounds that IRQs protect
> nothing and assumes the existing hotplug paths guarantees the PCP cannot be
> used after zone_pcp_enable(). That should be the case already because all
> the pages have been freed and there is no page to put on the PCP lists.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
--
Oscar Salvador
SUSE L3
prev parent reply other threads:[~2021-04-14 7:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 12:08 [PATCH v2 resend] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove Mel Gorman
2021-04-12 12:12 ` David Hildenbrand
2021-04-12 12:40 ` Vlastimil Babka
2021-04-12 14:08 ` Mel Gorman
2021-04-12 14:12 ` David Hildenbrand
2021-04-12 15:27 ` Mel Gorman
2021-04-12 16:02 ` David Hildenbrand
2021-04-13 9:36 ` Vlastimil Babka
2021-04-13 9:49 ` Mel Gorman
2021-04-13 10:16 ` Michal Hocko
2021-04-13 6:44 ` Michal Hocko
2021-04-13 6:40 ` Michal Hocko
2021-04-14 7:18 ` Oscar Salvador [this message]
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