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Subject[29/85] hw_breakpoint: Use cpu_possible_mask in {reserve,release}_bp_slot()
3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@redhat.com>

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: Ben Hutchings <ben@decadent.org.uk>
---
kernel/events/hw_breakpoint.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -147,7 +147,7 @@ fetch_bp_busy_slots(struct bp_busy_slots
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, bo
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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