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    SubjectRe: [PATCH] oprofile, perf: Use per-cpu framework
    On 06/22/2012 10:42 AM, Robert Richter wrote:
    > Will,
    >
    > On 15.06.12 17:19:54, Will Deacon wrote:
    >> On Fri, Jun 15, 2012 at 05:16:35PM +0100, Robert Richter wrote:
    >>> On 15.06.12 16:43:59, Will Deacon wrote:
    >>>> Given both the lack of feedback and the trivial nature of this patch would
    >>>> you be able to pick this up please? I'd rather not push it via the ARM tree
    >>>> as the change is under drivers/.
    >>>
    >>> Will, I will apply it. Sorry for not responding earlier.
    >
    > I just realized I wrote a patch some time ago that introduces per_cpu
    > variables, see below. Please give it a try to, I will then queue it
    > for v3.6.
    >
    > Your patch should go upstream anyway to make it into stable trees.
    >
    > Thanks,
    >
    > -Robert

    Hi Robert,

    I was able to build a linux-3.5.0-rc5+ kernel with this patch and the following troublesome config entry enabled:

    CONFIG_DEBUG_PER_CPU_MAPS=y

    The resulting kernel ran and oprofile functioned fine on a compulab trimslice machine.

    -Will

    >
    >
    > From f8bbfd7d28303967ca4e8597de9bdc9bf8b197e7 Mon Sep 17 00:00:00 2001
    > From: Robert Richter <robert.richter@amd.com>
    > Date: Thu, 23 Feb 2012 17:07:06 +0100
    > Subject: [PATCH] oprofile, perf: Use per-cpu framework
    >
    > This changes oprofile_perf.c to use the per-cpu framework.
    >
    > Using the per-cpu framework should avoid error like the following:
    >
    > arch/arm/oprofile/../../../drivers/oprofile/oprofile_perf.c:28:28: error: variably modified 'perf_events' at file scope
    >
    > Reported-by: William Cohen <wcohen@redhat.com>
    > Cc: Will Deacon <will.deacon@arm.com>
    > Signed-off-by: Robert Richter <robert.richter@amd.com>
    > ---
    > drivers/oprofile/oprofile_perf.c | 23 +++++++++++------------
    > 1 files changed, 11 insertions(+), 12 deletions(-)
    >
    > diff --git a/drivers/oprofile/oprofile_perf.c b/drivers/oprofile/oprofile_perf.c
    > index efc4b7f..f3cfa0b 100644
    > --- a/drivers/oprofile/oprofile_perf.c
    > +++ b/drivers/oprofile/oprofile_perf.c
    > @@ -1,5 +1,6 @@
    > /*
    > * Copyright 2010 ARM Ltd.
    > + * Copyright 2012 Advanced Micro Devices, Inc., Robert Richter
    > *
    > * Perf-events backend for OProfile.
    > */
    > @@ -25,7 +26,7 @@ static int oprofile_perf_enabled;
    > static DEFINE_MUTEX(oprofile_perf_mutex);
    >
    > static struct op_counter_config *counter_config;
    > -static struct perf_event **perf_events[NR_CPUS];
    > +static DEFINE_PER_CPU(struct perf_event **, perf_events);
    > static int num_counters;
    >
    > /*
    > @@ -38,7 +39,7 @@ static void op_overflow_handler(struct perf_event *event,
    > u32 cpu = smp_processor_id();
    >
    > for (id = 0; id < num_counters; ++id)
    > - if (perf_events[cpu][id] == event)
    > + if (per_cpu(perf_events, cpu)[id] == event)
    > break;
    >
    > if (id != num_counters)
    > @@ -74,7 +75,7 @@ static int op_create_counter(int cpu, int event)
    > {
    > struct perf_event *pevent;
    >
    > - if (!counter_config[event].enabled || perf_events[cpu][event])
    > + if (!counter_config[event].enabled || per_cpu(perf_events, cpu)[event])
    > return 0;
    >
    > pevent = perf_event_create_kernel_counter(&counter_config[event].attr,
    > @@ -91,18 +92,18 @@ static int op_create_counter(int cpu, int event)
    > return -EBUSY;
    > }
    >
    > - perf_events[cpu][event] = pevent;
    > + per_cpu(perf_events, cpu)[event] = pevent;
    >
    > return 0;
    > }
    >
    > static void op_destroy_counter(int cpu, int event)
    > {
    > - struct perf_event *pevent = perf_events[cpu][event];
    > + struct perf_event *pevent = per_cpu(perf_events, cpu)[event];
    >
    > if (pevent) {
    > perf_event_release_kernel(pevent);
    > - perf_events[cpu][event] = NULL;
    > + per_cpu(perf_events, cpu)[event] = NULL;
    > }
    > }
    >
    > @@ -257,12 +258,12 @@ void oprofile_perf_exit(void)
    >
    > for_each_possible_cpu(cpu) {
    > for (id = 0; id < num_counters; ++id) {
    > - event = perf_events[cpu][id];
    > + event = per_cpu(perf_events, cpu)[id];
    > if (event)
    > perf_event_release_kernel(event);
    > }
    >
    > - kfree(perf_events[cpu]);
    > + kfree(per_cpu(perf_events, cpu));
    > }
    >
    > kfree(counter_config);
    > @@ -277,8 +278,6 @@ int __init oprofile_perf_init(struct oprofile_operations *ops)
    > if (ret)
    > return ret;
    >
    > - memset(&perf_events, 0, sizeof(perf_events));
    > -
    > num_counters = perf_num_counters();
    > if (num_counters <= 0) {
    > pr_info("oprofile: no performance counters\n");
    > @@ -298,9 +297,9 @@ int __init oprofile_perf_init(struct oprofile_operations *ops)
    > }
    >
    > for_each_possible_cpu(cpu) {
    > - perf_events[cpu] = kcalloc(num_counters,
    > + per_cpu(perf_events, cpu) = kcalloc(num_counters,
    > sizeof(struct perf_event *), GFP_KERNEL);
    > - if (!perf_events[cpu]) {
    > + if (!per_cpu(perf_events, cpu)) {
    > pr_info("oprofile: failed to allocate %d perf events "
    > "for cpu %d\n", num_counters, cpu);
    > ret = -ENOMEM;



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