[ 3.5.y.z extended stable ] Patch "hw_breakpoint: Use cpu_possible_mask in" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    hw_breakpoint: Use cpu_possible_mask in

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5fa95301281656e4bc2d9651f0f5241b946c37d1 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg at redhat.com>
Date: Thu, 20 Jun 2013 17:50:09 +0200
Subject: [PATCH] hw_breakpoint: Use cpu_possible_mask in
 {reserve,release}_bp_slot()

commit c790b0ad23f427c7522ffed264706238c57c007e upstream.

fetch_bp_busy_slots() and toggle_bp_slot() use
for_each_online_cpu(), this is obviously wrong wrt cpu_up() or
cpu_down(), we can over/under account the per-cpu numbers.

For example:

	# echo 0 >> /sys/devices/system/cpu/cpu1/online
	# perf record -e mem:0x10 -p 1 &
	# echo 1 >> /sys/devices/system/cpu/cpu1/online
	# perf record -e mem:0x10,mem:0x10,mem:0x10,mem:0x10 -C1 -a &
	# taskset -p 0x2 1

triggers the same WARN_ONCE("Can't find any breakpoint slot") in
arch_install_hw_breakpoint().

Reported-by: Vince Weaver <vincent.weaver at maine.edu>
Signed-off-by: Oleg Nesterov <oleg at redhat.com>
Acked-by: Frederic Weisbecker <fweisbec at gmail.com>
Link: http://lkml.kernel.org/r/20130620155009.GA6327@redhat.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/events/hw_breakpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index bb38c4d..fc8bfcf 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -147,7 +147,7 @@ fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
 		return;
 	}

-	for_each_online_cpu(cpu) {
+	for_each_possible_cpu(cpu) {
 		unsigned int nr;

 		nr = per_cpu(nr_cpu_bp_pinned[type], cpu);
@@ -233,7 +233,7 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
 	if (cpu >= 0) {
 		toggle_bp_task_slot(bp, cpu, enable, type, weight);
 	} else {
-		for_each_online_cpu(cpu)
+		for_each_possible_cpu(cpu)
 			toggle_bp_task_slot(bp, cpu, enable, type, weight);
 	}

--
1.8.1.2