perf: Clarify perf_cpu_context::active_pmu usage by renaming it to ::unique_pmu

Stephane thought the perf_cpu_context::active_pmu name confusing and
suggested using 'unique_pmu' instead.

This pointer is a pointer to a 'random' pmu sharing the cpuctx
instance, therefore limiting a for_each_pmu loop to those where
cpuctx->unique_pmu matches the pmu we get a loop over unique cpuctx
instances.
Suggested-by: NStephane Eranian <eranian@google.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kxyjqpfj2fn9gt7kwu5ag9ks@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

include/linux/perf_event.h

@@ -1110,7 +1110,7 @@ struct perf_cpu_context {
 	int				exclusive;
 	struct list_head		rotation_list;
 	int				jiffies_interval;
-	struct pmu			*active_pmu;
+	struct pmu			*unique_pmu;
 	struct perf_cgroup		*cgrp;
 };
 

kernel/events/core.c

@@ -4419,7 +4419,7 @@ static void perf_event_task_event(struct perf_task_event *task_event)
 	rcu_read_lock();
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
 		cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
-		if (cpuctx->active_pmu != pmu)
+		if (cpuctx->unique_pmu != pmu)
 			goto next;
 		perf_event_task_ctx(&cpuctx->ctx, task_event);
 
@@ -4565,7 +4565,7 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
 	rcu_read_lock();
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
 		cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
-		if (cpuctx->active_pmu != pmu)
+		if (cpuctx->unique_pmu != pmu)
 			goto next;
 		perf_event_comm_ctx(&cpuctx->ctx, comm_event);
 
@@ -4761,7 +4761,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
 	rcu_read_lock();
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
 		cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
-		if (cpuctx->active_pmu != pmu)
+		if (cpuctx->unique_pmu != pmu)
 			goto next;
 		perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
 					vma->vm_flags & VM_EXEC);
@@ -5862,8 +5862,8 @@ static void update_pmu_context(struct pmu *pmu, struct pmu *old_pmu)
 
 		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
 
-		if (cpuctx->active_pmu == old_pmu)
-			cpuctx->active_pmu = pmu;
+		if (cpuctx->unique_pmu == old_pmu)
+			cpuctx->unique_pmu = pmu;
 	}
 }
 
@@ -5998,7 +5998,7 @@ int perf_pmu_register(struct pmu *pmu, char *name, int type)
 		cpuctx->ctx.pmu = pmu;
 		cpuctx->jiffies_interval = 1;
 		INIT_LIST_HEAD(&cpuctx->rotation_list);
-		cpuctx->active_pmu = pmu;
+		cpuctx->unique_pmu = pmu;
 	}
 
 got_cpu_context: