From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx174.postini.com [74.125.245.174]) by kanga.kvack.org (Postfix) with SMTP id 451786B006C for ; Sun, 22 Jul 2012 22:31:52 -0400 (EDT) Received: from /spool/local by e6.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 22 Jul 2012 22:31:51 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 119EC6E8039 for ; Sun, 22 Jul 2012 22:31:49 -0400 (EDT) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6N2VmtP191438 for ; Sun, 22 Jul 2012 22:31:48 -0400 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6N2VlY8023925 for ; Sun, 22 Jul 2012 20:31:47 -0600 From: Gavin Shan Subject: [PATCH RESEND v2 3/3] mm/sparse: remove index_init_lock Date: Mon, 23 Jul 2012 10:31:42 +0800 Message-Id: <1343010702-28720-3-git-send-email-shangw@linux.vnet.ibm.com> In-Reply-To: <1343010702-28720-1-git-send-email-shangw@linux.vnet.ibm.com> References: <1343010702-28720-1-git-send-email-shangw@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: mhocko@suse.cz, rientjes@google.com, akpm@linux-foundation.org, Gavin Shan 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 Reviewed-by: Michal Hocko --- mm/sparse.c | 14 +------------- 1 files changed, 1 insertions(+), 13 deletions(-) diff --git a/mm/sparse.c b/mm/sparse.c index 51950de..40b1100 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -77,7 +77,6 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid) static int __meminit sparse_index_init(unsigned long section_nr, int nid) { - static DEFINE_SPINLOCK(index_init_lock); unsigned long root = SECTION_NR_TO_ROOT(section_nr); struct mem_section *section; int ret = 0; @@ -88,20 +87,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid) section = sparse_index_alloc(nid); if (!section) return -ENOMEM; - /* - * This lock keeps two different sections from - * reallocating for the same index - */ - spin_lock(&index_init_lock); - - if (mem_section[root]) { - ret = -EEXIST; - goto out; - } mem_section[root] = section; -out: - spin_unlock(&index_init_lock); + return ret; } #else /* !SPARSEMEM_EXTREME */ -- 1.7.5.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org