x86/perf/intel/cstate: Sanitize error handling

There is no point in WARN_ON() inside of a well known init function. We
already know the call stack and it's really not of critical importance whether
the registration of a PMU fails.

Aside of that for consistency reasons it's just pointless to try to register
another PMU if the first register attempt failed. There is also no value in
keeping one PMU if the second one can not be registered.

Make it consistent so we can finaly modularize the driver.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20160320185623.579794064@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/events/intel/cstate.c

@@ -581,37 +581,45 @@ static int __init cstate_probe(const struct cstate_model *cm)
 	return (has_cstate_core || has_cstate_pkg) ? 0 : -ENODEV;
 }
 
-static void __init cstate_cpumask_init(void)
+static void __init cstate_cleanup(void)
 {
-	int cpu;
-
-	cpu_notifier_register_begin();
-
-	for_each_online_cpu(cpu)
-		cstate_cpu_init(cpu);
+	if (has_cstate_core)
+		perf_pmu_unregister(&cstate_core_pmu);
 
-	__perf_cpu_notifier(cstate_cpu_notifier);
-
-	cpu_notifier_register_done();
+	if (has_cstate_pkg)
+		perf_pmu_unregister(&cstate_pkg_pmu);
 }
 
-static void __init cstate_pmus_register(void)
+static int __init cstate_init(void)
 {
-	int err;
+	int cpu, err;
+
+	cpu_notifier_register_begin();
+	for_each_online_cpu(cpu)
+		cstate_cpu_init(cpu);
 
 	if (has_cstate_core) {
 		err = perf_pmu_register(&cstate_core_pmu, cstate_core_pmu.name, -1);
-		if (WARN_ON(err))
-			pr_info("Failed to register PMU %s error %d\n",
-				cstate_core_pmu.name, err);
+		if (err) {
+			has_cstate_core = false;
+			pr_info("Failed to register cstate core pmu\n");
+			goto out;
+		}
 	}
 
 	if (has_cstate_pkg) {
 		err = perf_pmu_register(&cstate_pkg_pmu, cstate_pkg_pmu.name, -1);
-		if (WARN_ON(err))
-			pr_info("Failed to register PMU %s error %d\n",
-				cstate_pkg_pmu.name, err);
+		if (err) {
+			has_cstate_pkg = false;
+			pr_info("Failed to register cstate pkg pmu\n");
+			cstate_cleanup();
+			goto out;
+		}
 	}
+	__perf_cpu_notifier(cstate_cpu_notifier);
+out:
+	cpu_notifier_register_done();
+	return err;
 }
 
 static int __init cstate_pmu_init(void)
@@ -630,10 +638,6 @@ static int __init cstate_pmu_init(void)
 	if (err)
 		return err;
 
-	cstate_cpumask_init();
-
-	cstate_pmus_register();
-
-	return 0;
+	return cstate_init();
 }
 device_initcall(cstate_pmu_init);