SYSCTL: Add a mutex to the page_alloc zone order sysctl
The zone list code clearly cannot tolerate concurrent writers (I couldn't
find any locks for that), so simply add a global mutex. No need for RCU
in this case.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d79b925..4e9f5cc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2402,13 +2402,14 @@
{
char saved_string[NUMA_ZONELIST_ORDER_LEN];
int ret;
+ static DEFINE_MUTEX(zl_order_mutex);
+ mutex_lock(&zl_order_mutex);
if (write)
- strncpy(saved_string, (char*)table->data,
- NUMA_ZONELIST_ORDER_LEN);
+ strcpy(saved_string, (char*)table->data);
ret = proc_dostring(table, write, buffer, length, ppos);
if (ret)
- return ret;
+ goto out;
if (write) {
int oldval = user_zonelist_order;
if (__parse_numa_zonelist_order((char*)table->data)) {
@@ -2421,7 +2422,9 @@
} else if (oldval != user_zonelist_order)
build_all_zonelists();
}
- return 0;
+out:
+ mutex_unlock(&zl_order_mutex);
+ return ret;
}