[PATCH 2/9] v3 Add mutex for adding/removing memory blocks

[Nathan Fontenot <nfont@austin.ibm.com>]

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: Nathan Fontenot <nfont@austin.ibm.com>

---
 drivers/base/memory.c |    7 +++++++
 1 file changed, 7 insertions(+)

Index: linux-next/drivers/base/memory.c
===================================================================
--- linux-next.orig/drivers/base/memory.c	2010-09-30 14:09:36.000000000 -0500
+++ linux-next/drivers/base/memory.c	2010-09-30 14:12:41.000000000 -0500
@@ -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 = {
@@ -476,6 +478,8 @@
 	if (!mem)
 		return -ENOMEM;
 
+	mutex_lock(&mem_sysfs_mutex);
+
 	mem->phys_index = __section_nr(section);
 	mem->state = state;
 	mutex_init(&mem->state_mutex);
@@ -496,6 +500,7 @@
 			ret = register_mem_sect_under_node(mem, nid);
 	}
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return ret;
 }
 
@@ -504,6 +509,7 @@
 {
 	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);
@@ -512,6 +518,7 @@
 	mem_remove_simple_file(mem, removable);
 	unregister_memory(mem, section);
 
+	mutex_unlock(&mem_sysfs_mutex);
 	return 0;
 }