From: Cong Wang <xiyou.wangcong@gmail.com>
To: linux-mm@kvack.org
Subject: Re: [PATCH RESEND v2 3/3] mm/sparse: remove index_init_lock
Date: Mon, 23 Jul 2012 08:20:18 +0000 (UTC) [thread overview]
Message-ID: <juj1g2$qh3$2@dough.gmane.org> (raw)
In-Reply-To: 1343010702-28720-3-git-send-email-shangw@linux.vnet.ibm.com
On Mon, 23 Jul 2012 at 02:31 GMT, Gavin Shan <shangw@linux.vnet.ibm.com> wrote:
> sparse_index_init uses index_init_lock spinlock to protect root
> mem_section assignment. The lock is not necessary anymore because the
> function is called only during the boot (during paging init which
> is executed only from a single CPU) and from the hotplug code (by
> add_memory via arch_add_memory) which uses mem_hotplug_mutex.
>
> The lock has been introduced by 28ae55c9 (sparsemem extreme: hotplug
> preparation) and sparse_index_init was used only during boot at that
> time.
>
> Later when the hotplug code (and add_memory) was introduced there was
> no synchronization so it was possible to online more sections from
> the same root probably (though I am not 100% sure about that).
> The first synchronization has been added by 6ad696d2 (mm: allow memory
> hotplug and hibernation in the same kernel) which has been later
> replaced by the mem_hotplug_mutex - 20d6c96b (mem-hotplug: introduce
> {un}lock_memory_hotplug()).
>
> Let's remove the lock as it is not needed and it makes the code more
> confusing.
>
> [mhocko@suse.cz: changelog]
> Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
> Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
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next prev parent reply other threads:[~2012-07-23 8:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-23 2:31 [PATCH RESEND v4 1/3] mm/sparse: optimize sparse_index_alloc Gavin Shan
2012-07-23 2:31 ` [PATCH RESEND v4 2/3] mm/sparse: more check on mem_section number Gavin Shan
2012-07-23 8:21 ` Cong Wang
2012-07-23 2:31 ` [PATCH RESEND v2 3/3] mm/sparse: remove index_init_lock Gavin Shan
2012-07-23 8:20 ` Cong Wang [this message]
2012-07-23 8:18 ` [PATCH RESEND v4 1/3] mm/sparse: optimize sparse_index_alloc Cong Wang
2012-07-24 0:54 ` Gavin Shan
2012-07-24 0:54 ` Gavin Shan
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