ARM: perf: lock PMU registers per-CPU

Currently, a single lock serialises access to CPU PMU registers. This
global locking is unnecessary as PMU registers are local to the CPU
they monitor.

This patch replaces the global lock with a per-CPU lock. As the lock is
in struct cpu_hw_events, PMUs providing a single cpu_hw_events instance
can be locked globally.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Ashwin Chaugule <ashwinc@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 15 insertions, 10 deletions

diff --git a/arch/arm/kernel/perf_event_v6.c b/arch/arm/kernel/perf_event_v6.c
index 839012862264..68cf70425f2f 100644
--- a/arch/arm/kernel/perf_event_v6.c
+++ b/arch/arm/kernel/perf_event_v6.c
@@ -433,6 +433,7 @@ armv6pmu_enable_event(struct hw_perf_event *hwc,
                       int idx)
 {
         unsigned long val, mask, evt, flags;
+        struct cpu_hw_events *events = armpmu->get_hw_events();
 
         if (ARMV6_CYCLE_COUNTER == idx) {
                 mask    = 0;
@@ -454,12 +455,12 @@ armv6pmu_enable_event(struct hw_perf_event *hwc,
          * Mask out the current event and set the counter to count the event
          * that we're interested in.
          */
-        raw_spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&events->pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        raw_spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }
 
 static int counter_is_active(unsigned long pmcr, int idx)
@@ -544,24 +545,26 @@ static void
 armv6pmu_start(void)
 {
         unsigned long flags, val;
+        struct cpu_hw_events *events = armpmu->get_hw_events();
 
-        raw_spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&events->pmu_lock, flags);
         val = armv6_pmcr_read();
         val |= ARMV6_PMCR_ENABLE;
         armv6_pmcr_write(val);
-        raw_spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }
 
 static void
 armv6pmu_stop(void)
 {
         unsigned long flags, val;
+        struct cpu_hw_events *events = armpmu->get_hw_events();
 
-        raw_spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&events->pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~ARMV6_PMCR_ENABLE;
         armv6_pmcr_write(val);
-        raw_spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }
 
 static int
@@ -595,6 +598,7 @@ armv6pmu_disable_event(struct hw_perf_event *hwc,
                        int idx)
 {
         unsigned long val, mask, evt, flags;
+        struct cpu_hw_events *events = armpmu->get_hw_events();
 
         if (ARMV6_CYCLE_COUNTER == idx) {
                 mask    = ARMV6_PMCR_CCOUNT_IEN;
@@ -615,12 +619,12 @@ armv6pmu_disable_event(struct hw_perf_event *hwc,
          * of ETM bus signal assertion cycles. The external reporting should
          * be disabled and so this should never increment.
          */
-        raw_spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&events->pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        raw_spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }
 
 static void
@@ -628,6 +632,7 @@ armv6mpcore_pmu_disable_event(struct hw_perf_event *hwc,
                               int idx)
 {
         unsigned long val, mask, flags, evt = 0;
+        struct cpu_hw_events *events = armpmu->get_hw_events();
 
         if (ARMV6_CYCLE_COUNTER == idx) {
                 mask    = ARMV6_PMCR_CCOUNT_IEN;
@@ -644,12 +649,12 @@ armv6mpcore_pmu_disable_event(struct hw_perf_event *hwc,
          * Unlike UP ARMv6, we don't have a way of stopping the counters. We
          * simply disable the interrupt reporting.
          */
-        raw_spin_lock_irqsave(&pmu_lock, flags);
+        raw_spin_lock_irqsave(&events->pmu_lock, flags);
         val = armv6_pmcr_read();
         val &= ~mask;
         val |= evt;
         armv6_pmcr_write(val);
-        raw_spin_unlock_irqrestore(&pmu_lock, flags);
+        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
 }
 
 static struct arm_pmu armv6pmu = {