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perf_counter: pmc arbitration 

Follow the example set by powerpc and try to play nice with oprofile
and the nmi watchdog.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.459968444@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-30 19:07:16 +02:00 committed by Ingo Molnar
parent d7d59fb323
commit 4e935e4717
1 changed files with 75 additions and 0 deletions
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75
arch/x86/kernel/cpu/perf_counter.c
View File

@ -20,6 +20,7 @@
#include <asm/apic.h>
#include <asm/stacktrace.h>
#include <asm/nmi.h>
static bool perf_counters_initialized __read_mostly;
@ -172,6 +173,65 @@ again:
atomic64_sub(delta, &hwc->period_left);
}
static atomic_t num_counters;
static DEFINE_MUTEX(pmc_reserve_mutex);
static bool reserve_pmc_hardware(void)
{
int i;
if (nmi_watchdog == NMI_LOCAL_APIC)
disable_lapic_nmi_watchdog();
for (i = 0; i < nr_counters_generic; i++) {
if (!reserve_perfctr_nmi(pmc_ops->perfctr + i))
goto perfctr_fail;
}
for (i = 0; i < nr_counters_generic; i++) {
if (!reserve_evntsel_nmi(pmc_ops->eventsel + i))
goto eventsel_fail;
}
return true;
eventsel_fail:
for (i--; i >= 0; i--)
release_evntsel_nmi(pmc_ops->eventsel + i);
i = nr_counters_generic;
perfctr_fail:
for (i--; i >= 0; i--)
release_perfctr_nmi(pmc_ops->perfctr + i);
if (nmi_watchdog == NMI_LOCAL_APIC)
enable_lapic_nmi_watchdog();
return false;
}
static void release_pmc_hardware(void)
{
int i;
for (i = 0; i < nr_counters_generic; i++) {
release_perfctr_nmi(pmc_ops->perfctr + i);
release_evntsel_nmi(pmc_ops->eventsel + i);
}
if (nmi_watchdog == NMI_LOCAL_APIC)
enable_lapic_nmi_watchdog();
}
static void hw_perf_counter_destroy(struct perf_counter *counter)
{
if (atomic_dec_and_mutex_lock(&num_counters, &pmc_reserve_mutex)) {
release_pmc_hardware();
mutex_unlock(&pmc_reserve_mutex);
}
}
/*
* Setup the hardware configuration for a given hw_event_type
*/
@ -179,10 +239,23 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
{
struct perf_counter_hw_event *hw_event = &counter->hw_event;
struct hw_perf_counter *hwc = &counter->hw;
int err;
if (unlikely(!perf_counters_initialized))
return -EINVAL;
err = 0;
if (atomic_inc_not_zero(&num_counters)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&num_counters) == 0 && !reserve_pmc_hardware())
err = -EBUSY;
else
atomic_inc(&num_counters);
mutex_unlock(&pmc_reserve_mutex);
}
if (err)
return err;
/*
* Generate PMC IRQs:
* (keep 'enabled' bit clear for now)
@ -230,6 +303,8 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
hwc->config |= pmc_ops->event_map(perf_event_id(hw_event));
}
counter->destroy = hw_perf_counter_destroy;
return 0;
}