Patchwork [3.8.y.z,extended,stable] Patch "hw_breakpoint: Use cpu_possible_mask in {reserve, release}_bp_slot()" has been added to staging queue

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Submitter Kamal Mostafa
Date June 26, 2013, 11:43 p.m.
Message ID <1372290223-14743-1-git-send-email-kamal@canonical.com>
Download mbox | patch
Permalink /patch/254922/
State New
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Comments

Kamal Mostafa - June 26, 2013, 11:43 p.m.
This is a note to let you know that I have just added a patch titled

    hw_breakpoint: Use cpu_possible_mask in {reserve,release}_bp_slot()

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.4.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

From d61896f7e400141415f6898f25cc6e394ce195e8 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Thu, 20 Jun 2013 17:50:09 +0200
Subject: 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@maine.edu>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155009.GA6327@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 kernel/events/hw_breakpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--
1.8.1.2

Patch

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 4a99beb..c3a1b86 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -149,7 +149,7 @@  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);
@@ -235,7 +235,7 @@  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);
 	}