linux-kernel - [tip:perf/core] hw_breakpoint: Use cpu_possible_mask in {reserve, release}_bp

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Date:	Thu, 20 Jun 2013 09:18:46 -0700
From:	tip-bot for Oleg Nesterov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	stable@...r.kernel.org, vincent.weaver@...ne.edu,
	fweisbec@...il.com, tglx@...utronix.de, oleg@...hat.com
Subject: [tip:perf/core] hw_breakpoint: Use cpu_possible_mask in {reserve,
 release}_bp_slot()

Commit-ID:  c790b0ad23f427c7522ffed264706238c57c007e
Gitweb:     http://git.kernel.org/tip/c790b0ad23f427c7522ffed264706238c57c007e
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Thu, 20 Jun 2013 17:50:09 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 20 Jun 2013 17:57:01 +0200

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

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@...ne.edu>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: <stable@...r.kernel.org>
Link: http://lkml.kernel.org/r/20130620155009.GA6327@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 a853dea..20185ea 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);
 	}
 
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