Driver core: Add mutex for adding/removing memory blocks

Add a new mutex for use in adding and removing of memory blocks.  This
is needed to avoid any race conditions in which the same memory block could
be added and removed at the same time.
Signed-off-by: NNathan Fontenot <nfont@austin.ibm.com>
Reviewed-by: NRobin Holt <holt@sgi.com>
Reviewed-By: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/base/memory.c

@@ -27,6 +27,8 @@
 #include <asm/atomic.h>
 #include <asm/uaccess.h>
 
+static DEFINE_MUTEX(mem_sysfs_mutex);
+
 #define MEMORY_CLASS_NAME	"memory"
 
 static struct sysdev_class memory_sysdev_class = {
@@ -484,6 +486,8 @@ static int add_memory_block(int nid, struct mem_section *section,
 	if (!mem)
 		return -ENOMEM;
 
+	mutex_lock(&mem_sysfs_mutex);
+
 	mem->phys_index = __section_nr(section);
 	mem->state = state;
 	mutex_init(&mem->state_mutex);
@@ -504,6 +508,7 @@ static int add_memory_block(int nid, struct mem_section *section,
 			ret = register_mem_sect_under_node(mem, nid);
 	}
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return ret;
 }
 
@@ -512,6 +517,7 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
 {
 	struct memory_block *mem;
 
+	mutex_lock(&mem_sysfs_mutex);
 	mem = find_memory_block(section);
 	unregister_mem_sect_under_nodes(mem);
 	mem_remove_simple_file(mem, phys_index);
@@ -520,6 +526,7 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
 	mem_remove_simple_file(mem, removable);
 	unregister_memory(mem, section);
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return 0;
 }