From: Cody P Schafer <cody@linux.vnet.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/4] memory_hotplug: use pgdat_resize_lock() when updating node_present_pages
Date: Wed, 01 May 2013 15:41:02 -0700 [thread overview]
Message-ID: <518199FE.7060908@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1305011530050.8804@chino.kir.corp.google.com>
On 05/01/2013 03:30 PM, David Rientjes wrote:
> On Wed, 1 May 2013, Cody P Schafer wrote:
>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index a221fac..0bdca10 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -915,6 +915,7 @@ static void node_states_set_node(int node, struct memory_notify *arg)
>>
>> int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
>> {
>> + unsigned long flags;
>> unsigned long onlined_pages = 0;
>> struct zone *zone;
>> int need_zonelists_rebuild = 0;
>> @@ -993,7 +994,11 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
>>
>> zone->managed_pages += onlined_pages;
>> zone->present_pages += onlined_pages;
>> +
>> + pgdat_resize_lock(zone->zone_pgdat, &flags);
>> zone->zone_pgdat->node_present_pages += onlined_pages;
>> + pgdat_resize_unlock(zone->zone_pgdat, &flags);
>> +
>> if (onlined_pages) {
>> node_states_set_node(zone_to_nid(zone), &arg);
>> if (need_zonelists_rebuild)
>
> Why? You can't get a partial read of a word-sized data structure.
>
Guaranteed to be stable means that if I'm a reader and
pgdat_resize_lock(), node_present_pages had better not change at all
until I pgdat_resize_unlock().
If nothing needs this guarantee, we should change the rules of
pgdat_resize_lock(). I played it safe and went with following the
existing rules.
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next prev parent reply other threads:[~2013-05-01 22:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-01 22:17 [PATCH 0/4] misc patches related to resizing nodes & zones Cody P Schafer
2013-05-01 22:17 ` [PATCH 1/4] mmzone: make holding lock_memory_hotplug() a requirement for updating pgdat size Cody P Schafer
2013-05-01 22:26 ` David Rientjes
2013-05-01 22:32 ` Cody P Schafer
2013-05-01 22:39 ` David Rientjes
2013-05-01 22:45 ` Cody P Schafer
2013-05-01 22:17 ` [PATCH 2/4] mm: fix comment referring to non-existent size_seqlock, change to span_seqlock Cody P Schafer
2013-05-01 22:27 ` David Rientjes
2013-05-01 22:17 ` [PATCH 3/4] mmzone: note that node_size_lock should be manipulated via pgdat_resize_lock() Cody P Schafer
2013-05-01 22:29 ` David Rientjes
2013-05-01 22:36 ` Cody P Schafer
2013-05-01 22:42 ` David Rientjes
2013-05-01 22:47 ` Cody P Schafer
2013-05-01 22:17 ` [PATCH 4/4] memory_hotplug: use pgdat_resize_lock() when updating node_present_pages Cody P Schafer
2013-05-01 22:30 ` David Rientjes
2013-05-01 22:41 ` Cody P Schafer [this message]
2013-05-01 22:48 ` David Rientjes
2013-05-01 22:51 ` Cody P Schafer
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