memory hotplug: one more lock on memory hotplug (925268a0) · Commits · 戴 / test

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>

include/linux/memory_hotplug.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -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);

mm/memory_hotplug.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

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