mm/hotplug: remove stop_machine() from try_offline_node()
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>
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 247d666..d595606 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1695,9 +1695,8 @@
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 @@
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 @@
#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 @@
* 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 @@
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 @@
}
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;