perf: Add helper function to return number of counters

The number of counters for the registered pmu is needed in a few places
so provide a helper function that returns this number.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Tested-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Robert Richter <robert.richter@amd.com>

4 files changed, 34 insertions, 13 deletions

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 417c392ddf1c..3b0aedfb96e7 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -123,6 +123,12 @@ armpmu_get_max_events(void)
 }
 EXPORT_SYMBOL_GPL(armpmu_get_max_events);
 
+int perf_num_counters(void)
+{
+        return armpmu_get_max_events();
+}
+EXPORT_SYMBOL_GPL(perf_num_counters);
+
 #define HW_OP_UNSUPPORTED               0xFFFF
 
 #define C(_x) \
diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index d660cb8dab36..1e971a7fcf82 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c
@@ -43,7 +43,7 @@ static DEFINE_MUTEX(op_arm_mutex);
 
 static struct op_counter_config *counter_config;
 static struct perf_event **perf_events[nr_cpumask_bits];
-static int perf_num_counters;
+static int num_counters;
 
 /*
  * Overflow callback for oprofile.
@@ -54,11 +54,11 @@ static void op_overflow_handler(struct perf_event *event, int unused,
         int id;
         u32 cpu = smp_processor_id();
 
-        for (id = 0; id < perf_num_counters; ++id)
+        for (id = 0; id < num_counters; ++id)
                 if (perf_events[cpu][id] == event)
                         break;
 
-        if (id != perf_num_counters)
+        if (id != num_counters)
                 oprofile_add_sample(regs, id);
         else
                 pr_warning("oprofile: ignoring spurious overflow "
@@ -76,7 +76,7 @@ static void op_perf_setup(void)
         u32 size = sizeof(struct perf_event_attr);
         struct perf_event_attr *attr;
 
-        for (i = 0; i < perf_num_counters; ++i) {
+        for (i = 0; i < num_counters; ++i) {
                 attr = &counter_config[i].attr;
                 memset(attr, 0, size);
                 attr->type              = PERF_TYPE_RAW;
@@ -131,7 +131,7 @@ static int op_perf_start(void)
         int cpu, event, ret = 0;
 
         for_each_online_cpu(cpu) {
-                for (event = 0; event < perf_num_counters; ++event) {
+                for (event = 0; event < num_counters; ++event) {
                         ret = op_create_counter(cpu, event);
                         if (ret)
                                 goto out;
@@ -150,7 +150,7 @@ static void op_perf_stop(void)
         int cpu, event;
 
         for_each_online_cpu(cpu)
-                for (event = 0; event < perf_num_counters; ++event)
+                for (event = 0; event < num_counters; ++event)
                         op_destroy_counter(cpu, event);
 }
 
@@ -179,7 +179,7 @@ static int op_arm_create_files(struct super_block *sb, struct dentry *root)
 {
         unsigned int i;
 
-        for (i = 0; i < perf_num_counters; i++) {
+        for (i = 0; i < num_counters; i++) {
                 struct dentry *dir;
                 char buf[4];
 
@@ -353,14 +353,19 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
 
         memset(&perf_events, 0, sizeof(perf_events));
 
-        perf_num_counters = armpmu_get_max_events();
+        num_counters = perf_num_counters();
+        if (num_counters <= 0) {
+                pr_info("oprofile: no performance counters\n");
+                ret = -ENODEV;
+                goto out;
+        }
 
-        counter_config = kcalloc(perf_num_counters,
+        counter_config = kcalloc(num_counters,
                         sizeof(struct op_counter_config), GFP_KERNEL);
 
         if (!counter_config) {
                 pr_info("oprofile: failed to allocate %d "
-                                "counters\n", perf_num_counters);
+                                "counters\n", num_counters);
                 ret = -ENOMEM;
                 goto out;
         }
@@ -370,11 +375,11 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
                 goto out;
 
         for_each_possible_cpu(cpu) {
-                perf_events[cpu] = kcalloc(perf_num_counters,
+                perf_events[cpu] = kcalloc(num_counters,
                                 sizeof(struct perf_event *), GFP_KERNEL);
                 if (!perf_events[cpu]) {
                         pr_info("oprofile: failed to allocate %d perf events "
-                                        "for cpu %d\n", perf_num_counters, cpu);
+                                        "for cpu %d\n", num_counters, cpu);
                         ret = -ENOMEM;
                         goto out;
                 }
@@ -409,7 +414,7 @@ void __exit oprofile_arch_exit(void)
         struct perf_event *event;
 
         for_each_possible_cpu(cpu) {
-                for (id = 0; id < perf_num_counters; ++id) {
+                for (id = 0; id < num_counters; ++id) {
                         event = perf_events[cpu][id];
                         if (event)
                                 perf_event_release_kernel(event);
diff --git a/arch/sh/kernel/perf_event.c b/arch/sh/kernel/perf_event.c
index 7a3dc3567258..2cb9ad59d4b1 100644
--- a/arch/sh/kernel/perf_event.c
+++ b/arch/sh/kernel/perf_event.c
@@ -59,6 +59,15 @@ static inline int sh_pmu_initialized(void)
         return !!sh_pmu;
 }
 
+int perf_num_counters(void)
+{
+        if (!sh_pmu)
+                return 0;
+
+        return sh_pmu->num_events;
+}
+EXPORT_SYMBOL_GPL(perf_num_counters);
+
 /*
  * Release the PMU if this is the last perf_event.
  */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 716f99b682c1..1a0219247183 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -849,6 +849,7 @@ extern int perf_max_events;
 
 extern const struct pmu *hw_perf_event_init(struct perf_event *event);
 
+extern int perf_num_counters(void);
 extern void perf_event_task_sched_in(struct task_struct *task);
 extern void perf_event_task_sched_out(struct task_struct *task, struct task_struct *next);
 extern void perf_event_task_tick(struct task_struct *task);