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mm/hotplug: remove stop_machine() from try_offline_node()

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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>
This commit is contained in:
Toshi Kani 2013-09-11 14:21:50 -07:00 committed by Linus Torvalds
parent 27356f54c8
commit 0f1cfe9d0d
1 changed files with 22 additions and 9 deletions
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31
mm/memory_hotplug.c
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@ -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;