2 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/memory.h b/include/linux/memory.h
index 3fdc10806d31..86a6c0f0518d 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -99,4 +99,10 @@ enum mem_add_context { BOOT, HOTPLUG };
 #define hotplug_memory_notifier(fn, pri) do { } while (0)
 #endif
 
+/*
+ * Kernel text modification mutex, used for code patching. Users of this lock
+ * can sleep.
+ */
+extern struct mutex text_mutex;
+
 #endif /* _LINUX_MEMORY_H_ */
diff --git a/mm/memory.c b/mm/memory.c
index baa999e87cd2..05fab3bc5b4b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -48,6 +48,8 @@
 #include <linux/rmap.h>
 #include <linux/module.h>
 #include <linux/delayacct.h>
+#include <linux/kprobes.h>
+#include <linux/mutex.h>
 #include <linux/init.h>
 #include <linux/writeback.h>
 #include <linux/memcontrol.h>
@@ -99,6 +101,14 @@ int randomize_va_space __read_mostly =
                                         2;
 #endif
 
+/*
+ * mutex protecting text section modification (dynamic code patching).
+ * some users need to sleep (allocating memory...) while they hold this lock.
+ *
+ * NOT exported to modules - patching kernel text is a really delicate matter.
+ */
+DEFINE_MUTEX(text_mutex);
+
 static int __init disable_randmaps(char *s)
 {
         randomize_va_space = 0;