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memory hotplug: one more lock on memory hotplug 

Now, memory_hotplug_(un)lock() is used for add/remove/offline pages
for avoiding races with hibernation. But this should be held in
online_pages(), too. It seems asymmetric.

There are cases where one has to avoid a race with memory hotplug
notifier and his own local code, and hotplug v.s. hotplug.
This will add a generic solution for avoiding races. In other view,
having lock here has no big impacts. online pages is tend to be
done by udev script at el against each memory section one by one.

Then, it's better to have lock here, too.

Cc: <stable@kernel.org> # 2.6.37
Reviewed-by: Christoph Lameter <cl@linux.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2011-01-11 16:44:01 +09:00 committed by Pekka Enberg
parent 3c0eee3fe6
commit 925268a06d
2 changed files with 10 additions and 0 deletions
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6
include/linux/memory_hotplug.h
View File

@ -161,6 +161,12 @@ extern void register_page_bootmem_info_node(struct pglist_data *pgdat);
extern void put_page_bootmem(struct page *page);
#endif
/*
* Lock for memory hotplug guarantees 1) all callbacks for memory hotplug
* notifier will be called under this. 2) offline/online/add/remove memory
* will not run simultaneously.
*/
void lock_memory_hotplug(void);
void unlock_memory_hotplug(void);

4
mm/memory_hotplug.c
View File

@ -407,6 +407,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
int ret;
struct memory_notify arg;
lock_memory_hotplug();
arg.start_pfn = pfn;
arg.nr_pages = nr_pages;
arg.status_change_nid = -1;
@ -419,6 +420,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
ret = notifier_to_errno(ret);
if (ret) {
memory_notify(MEM_CANCEL_ONLINE, &arg);
unlock_memory_hotplug();
return ret;
}
/*
@ -443,6 +445,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
nr_pages, pfn);
memory_notify(MEM_CANCEL_ONLINE, &arg);
unlock_memory_hotplug();
return ret;
}
@ -467,6 +470,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
if (onlined_pages)
memory_notify(MEM_ONLINE, &arg);
unlock_memory_hotplug();
return 0;
}