Patch "PM / sleep / x86: Fix crash on graph trace through x86 suspend" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

PM / sleep / x86: Fix crash on graph trace through x86 suspend

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pm-sleep-x86-fix-crash-on-graph-trace-through-x86-suspend.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Todd E Brandt <[email protected]>
Date: Wed, 2 Mar 2016 16:05:29 -0800
Subject: PM / sleep / x86: Fix crash on graph trace through x86 suspend

From: Todd E Brandt <[email protected]>

commit 92f9e179a702a6adbc11e2fedc76ecd6ffc9e3f7 upstream.

Pause/unpause graph tracing around do_suspend_lowlevel as it has inconsistent call/return info after it jumps to the wakeup vector. The graph trace buffer will otherwise become misaligned and may eventually crash and hang on suspend.

To reproduce the issue and test the fix:
Run a function_graph trace over suspend/resume and set the graph function to suspend_devices_and_enter. This consistently hangs the system without this fix.

---
 arch/x86/kernel/acpi/sleep.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -16,6 +16,7 @@
 #include <asm/cacheflush.h>
 #include <asm/realmode.h>
 
+#include <linux/ftrace.h>
 #include "../../realmode/rm/wakeup.h"
 #include "sleep.h"
 

@@ -107,7 +108,13 @@ int x86_acpi_suspend_lowlevel(void)
        saved_magic = 0x123456789abcdef0L;
 #endif /* CONFIG_64BIT */
 
+	/*
+	 * Pause/unpause graph tracing around do_suspend_lowlevel as it has
+	 * inconsistent call/return info after it jumps to the wakeup vector.
+	 */
+	pause_graph_tracing();
 	do_suspend_lowlevel();
+	unpause_graph_tracing();
 	return 0;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/pm-sleep-x86-fix-crash-on-graph-trace-through-x86-suspend.patch