Patch "x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm" 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

x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm

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:
x86-perf-fix-cr4.pce-propagation-to-use-active_mm-instead-of-mm.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: Andy Lutomirski <[email protected]>
Date: Thu, 16 Mar 2017 12:59:39 -0700
Subject: x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm

From: Andy Lutomirski <[email protected]>

commit 5dc855d44c2ad960a86f593c60461f1ae1566b6d upstream.

If one thread mmaps a perf event while another thread in the same mm is in some context where active_mm != mm (which can happen in the scheduler, for example), refresh_pce() would write the wrong value to CR4.PCE. This broke some PAPI tests.

---
 arch/x86/kernel/cpu/perf_event.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -1996,8 +1996,8 @@ static int x86_pmu_event_init(struct per
 
 static void refresh_pce(void *ignored)
 {
-	if (current->mm)
-		load_mm_cr4(current->mm);
+	if (current->active_mm)
+		load_mm_cr4(current->active_mm);
 }
 
 static void x86_pmu_event_mapped(struct perf_event *event)

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

queue-4.4/x86-perf-fix-cr4.pce-propagation-to-use-active_mm-instead-of-mm.patch