mm/hotplug: remove stop_machine() from try_offline_node() (0f1cfe9d) · Commits · 戴 / test

lock_device_hotplug() serializes hotplug & online/offline operations. The lock is held in common sysfs online/offline interfaces and ACPI hotplug code paths. And here are the code paths: - CPU & Mem online/offline via sysfs online store_online()->lock_device_hotplug() - Mem online via sysfs state: store_mem_state()->lock_device_hotplug() - ACPI CPU & Mem hot-add: acpi_scan_bus_device_check()->lock_device_hotplug() - ACPI CPU & Mem hot-delete: acpi_scan_hot_remove()->lock_device_hotplug() try_offline_node() off-lines a node if all memory sections and cpus are removed on the node. It is called from acpi_processor_remove() and acpi_memory_remove_memory()->remove_memory() paths, both of which are in the ACPI hotplug code. try_offline_node() calls stop_machine() to stop all cpus while checking all cpu status with the assumption that the caller is not protected from CPU hotplug or CPU online/offline operations. However, the caller is always serialized with lock_device_hotplug(). Also, the code needs to be properly serialized with a lock, not by stopping all cpus at a random place with stop_machine(). This patch removes the use of stop_machine() in try_offline_node() and adds comments to try_offline_node() and remove_memory() that lock_device_hotplug() is required. Signed-off-by:

Toshi Kani <toshi.kani@hp.com> Acked-by:

Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Tang Chen <tangchen@cn.fujitsu.com> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

+22 −9

Original line number	Diff line number	Diff line
		@@ -1695,9 +1695,8 @@ static int is_memblock_offlined_cb(struct memory_block mem, void arg)
		return ret;
		}

		static int check_cpu_on_node(void *data)
		static int check_cpu_on_node(pg_data_t *pgdat)
		{
		struct pglist_data *pgdat = data;
		int cpu;

		for_each_present_cpu(cpu) {
		@@ -1712,10 +1711,9 @@ static int check_cpu_on_node(void *data)
		return 0;
		}

		static void unmap_cpu_on_node(void *data)
		static void unmap_cpu_on_node(pg_data_t *pgdat)
		{
		#ifdef CONFIG_ACPI_NUMA
		struct pglist_data *pgdat = data;
		int cpu;

		for_each_possible_cpu(cpu)
		@@ -1724,10 +1722,11 @@ static void unmap_cpu_on_node(void *data)
		#endif
		}

		static int check_and_unmap_cpu_on_node(void *data)
		static int check_and_unmap_cpu_on_node(pg_data_t *pgdat)
		{
		int ret = check_cpu_on_node(data);
		int ret;

		ret = check_cpu_on_node(pgdat);
		if (ret)
		return ret;

		@@ -1736,11 +1735,18 @@ static int check_and_unmap_cpu_on_node(void *data)
		* the cpu_to_node() now.
		*/

		unmap_cpu_on_node(data);
		unmap_cpu_on_node(pgdat);
		return 0;
		}

		/* offline the node if all memory sections of this node are removed */
		/**
		* try_offline_node
		*
		* Offline a node if all memory sections and cpus of the node are removed.
		*
		* NOTE: The caller must call lock_device_hotplug() to serialize hotplug
		* and online/offline operations before this call.
		*/
		void try_offline_node(int nid)
		{
		pg_data_t *pgdat = NODE_DATA(nid);
		@@ -1766,7 +1772,7 @@ void try_offline_node(int nid)
		return;
		}

		if (stop_machine(check_and_unmap_cpu_on_node, pgdat, NULL))
		if (check_and_unmap_cpu_on_node(pgdat))
		return;

		/*
		@@ -1803,6 +1809,13 @@ void try_offline_node(int nid)
		}
		EXPORT_SYMBOL(try_offline_node);

		/**
		* remove_memory
		*
		* NOTE: The caller must call lock_device_hotplug() to serialize hotplug
		* and online/offline operations before this call, as required by
		* try_offline_node().
		*/
		void __ref remove_memory(int nid, u64 start, u64 size)
		{
		int ret;

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