From 4e935e47177c3b26cf383e79849bae2a464d0160 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 30 Mar 2009 19:07:16 +0200 Subject: [PATCH] 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 Acked-by: Paul Mackerras Orig-LKML-Reference: <20090330171024.459968444@chello.nl> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_counter.c | 75 ++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index e16dfafc6d72..2a946a160cac 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -20,6 +20,7 @@ #include #include +#include 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; } -- 2.34.1