From: Michal Hocko <mhocko@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
LKML <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH] mm/memory-hotplug: Switch locking to a percpu rwsem
Date: Mon, 3 Jul 2017 18:32:04 +0200 [thread overview]
Message-ID: <20170703163204.GE11848@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.20.1706301210210.1748@nanos>
On Fri 30-06-17 12:15:21, Thomas Gleixner wrote:
[...]
> Sure. Just to make you to mull over more stuff, find below the patch which
> moves all of this to use the cpuhotplug lock.
>
> Thanks,
>
> tglx
>
> 8<--------------------
> Subject: mm/memory-hotplug: Use cpu hotplug lock
> From: Thomas Gleixner <tglx@linutronix.de>
> Date: Thu, 29 Jun 2017 16:30:00 +0200
>
> Most place which take the memory hotplug lock take the cpu hotplug lock as
> well. Avoid the double locking and use the cpu hotplug lock for both.
Hmm, I am usually not a fan of locks conflating because it is then less
clear what the lock actually protects. Memory and cpu hotplugs should
be largely independent so I am not sure this patch simplify things a
lot. It is nice to see few lines go away but I am little bit worried
that we will enventually develop a separate locking again in future for
some weird memory hotplug usecases.
> Not-Yet-Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[...]
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
[...]
> @@ -2138,7 +2114,7 @@ void __ref remove_memory(int nid, u64 st
>
> try_offline_node(nid);
>
> - mem_hotplug_done();
> + cpus_write_lock();
unlock you meant here, right?
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-07-03 16:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 16:11 [PATCH] mm/memory-hotplug: Switch locking to a percpu rwsem Thomas Gleixner
2017-06-30 9:27 ` Michal Hocko
2017-06-30 10:15 ` Thomas Gleixner
2017-06-30 11:49 ` Andrey Ryabinin
2017-06-30 13:00 ` Thomas Gleixner
2017-06-30 15:56 ` Andrey Ryabinin
2017-07-03 16:32 ` Michal Hocko [this message]
2017-07-03 19:57 ` Thomas Gleixner
2017-07-03 12:41 ` Vladimir Davydov
2017-07-03 16:38 ` Michal Hocko
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