This is an architecture independant synchronization around kernel text

modifications through use of a global mutex.
A mutex has been chosen so that kprobes, the main user of this, can sleep during

memory allocation between the memory read of the instructions it must replace

and the memory write of the breakpoint.
Other user of this interface: immediate values.
Paravirt and alternatives are always done when SMP is inactive, so there is no

need to use locks.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

CC: Andi Kleen <andi@firstfloor.org>

CC: Ingo Molnar <mingo@elte.hu>

---

 include/linux/memory.h |    7 +++++++

 mm/memory.c            |   34 ++++++++++++++++++++++++++++++++++

 2 files changed, 41 insertions(+)
Index: linux-2.6-lttng/include/linux/memory.h

===================================================================

--- linux-2.6-lttng.orig/include/linux/memory.h	2008-04-08 12:01:44.000000000 -0400

+++ linux-2.6-lttng/include/linux/memory.h	2008-04-08 12:01:56.000000000 -0400

@@ -93,4 +93,11 @@ extern int memory_notify(unsigned long v

 #define hotplug_memory_notifier(fn, pri) do { } while (0)

 #endif
+/*

+ * Take and release the kernel text modification lock, used for code patching.

+ * Users of this lock can sleep.

+ */

+extern void kernel_text_lock(void);

+extern void kernel_text_unlock(void);

+

 #endif /* _LINUX_MEMORY_H_ */

Index: linux-2.6-lttng/mm/memory.c

===================================================================

--- linux-2.6-lttng.orig/mm/memory.c	2008-04-08 12:01:44.000000000 -0400

+++ linux-2.6-lttng/mm/memory.c	2008-04-08 12:01:56.000000000 -0400

@@ -51,6 +51,8 @@

 #include <linux/init.h>

 #include <linux/writeback.h>

 #include <linux/memcontrol.h>

+#include <linux/kprobes.h>

+#include <linux/mutex.h>
 #include <asm/pgalloc.h>

 #include <asm/uaccess.h>

@@ -96,6 +98,12 @@ int randomize_va_space __read_mostly =

 					2;

 #endif
+/*

+ * mutex protec...
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