[patch V2 16/67] perf/x86/intel/cstate: Convert Intel CSTATE to hotplug state machine

[Anna-Maria Gleixner]

From: Sebastian Andrzej Siewior <bige...@linutronix.de>

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Borislav Petkov <b...@suse.de>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Kan Liang <kan.li...@intel.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephane Eranian <eran...@google.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Vince Weaver <vincent.wea...@maine.edu>
Cc: kbuild test robot <fengguang...@intel.com>
Signed-off-by: Anna-Maria Gleixner <anna-ma...@linutronix.de>
---
 arch/x86/events/intel/cstate.c | 51 +++++++++++++-----------------------------
 include/linux/cpuhotplug.h     |  2 ++
 2 files changed, 17 insertions(+), 36 deletions(-)

diff --git a/arch/x86/events/intel/cstate.c b/arch/x86/events/intel/cstate.c
index 9ba4e41..d6d7be0 100644
--- a/arch/x86/events/intel/cstate.c
+++ b/arch/x86/events/intel/cstate.c
@@ -365,7 +365,7 @@ static int cstate_pmu_event_add(struct perf_event *event, 
int mode)
  * Check if exiting cpu is the designated reader. If so migrate the
  * events when there is a valid target available
  */
-static void cstate_cpu_exit(int cpu)
+static int cstate_cpu_exit(unsigned int cpu)
 {
        unsigned int target;
 
@@ -390,9 +390,10 @@ static void cstate_cpu_exit(int cpu)
                        perf_pmu_migrate_context(&cstate_pkg_pmu, cpu, target);
                }
        }
+       return 0;
 }
 
-static void cstate_cpu_init(int cpu)
+static int cstate_cpu_init(unsigned int cpu)
 {
        unsigned int target;
 
@@ -414,31 +415,10 @@ static void cstate_cpu_init(int cpu)
                                 topology_core_cpumask(cpu));
        if (has_cstate_pkg && target >= nr_cpu_ids)
                cpumask_set_cpu(cpu, &cstate_pkg_cpu_mask);
-}
 
-static int cstate_cpu_notifier(struct notifier_block *self,
-                              unsigned long action, void *hcpu)
-{
-       unsigned int cpu = (long)hcpu;
-
-       switch (action & ~CPU_TASKS_FROZEN) {
-       case CPU_STARTING:
-               cstate_cpu_init(cpu);
-               break;
-       case CPU_DOWN_PREPARE:
-               cstate_cpu_exit(cpu);
-               break;
-       default:
-               break;
-       }
-       return NOTIFY_OK;
+       return 0;
 }
 
-static struct notifier_block cstate_cpu_nb = {
-       .notifier_call  = cstate_cpu_notifier,
-       .priority       = CPU_PRI_PERF + 1,
-};
-
 static struct pmu cstate_core_pmu = {
        .attr_groups    = core_attr_groups,
        .name           = "cstate_core",
@@ -599,18 +579,20 @@ static inline void cstate_cleanup(void)
 
 static int __init cstate_init(void)
 {
-       int cpu, err;
+       int err;
 
-       cpu_notifier_register_begin();
-       for_each_online_cpu(cpu)
-               cstate_cpu_init(cpu);
+       cpuhp_setup_state(CPUHP_AP_PERF_X86_CSTATE_STARTING,
+                         "AP_PERF_X86_CSTATE_STARTING", cstate_cpu_init,
+                         NULL);
+       cpuhp_setup_state(CPUHP_AP_PERF_X86_CSTATE_ONLINE,
+                         "AP_PERF_X86_CSTATE_ONLINE", NULL, cstate_cpu_exit);
 
        if (has_cstate_core) {
                err = perf_pmu_register(&cstate_core_pmu, cstate_core_pmu.name, 
-1);
                if (err) {
                        has_cstate_core = false;
                        pr_info("Failed to register cstate core pmu\n");
-                       goto out;
+                       return err;
                }
        }
 
@@ -620,12 +602,10 @@ static int __init cstate_init(void)
                        has_cstate_pkg = false;
                        pr_info("Failed to register cstate pkg pmu\n");
                        cstate_cleanup();
-                       goto out;
+                       return err;
                }
        }
-       __register_cpu_notifier(&cstate_cpu_nb);
-out:
-       cpu_notifier_register_done();
+
        return err;
 }
 
@@ -651,9 +631,8 @@ module_init(cstate_pmu_init);
 
 static void __exit cstate_pmu_exit(void)
 {
-       cpu_notifier_register_begin();
-       __unregister_cpu_notifier(&cstate_cpu_nb);
+       cpuhp_remove_state_nocalls(CPUHP_AP_PERF_X86_CSTATE_ONLINE);
+       cpuhp_remove_state_nocalls(CPUHP_AP_PERF_X86_CSTATE_STARTING);
        cstate_cleanup();
-       cpu_notifier_register_done();
 }
 module_exit(cstate_pmu_exit);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index f9399ee..68f4495 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -26,6 +26,7 @@ enum cpuhp_state {
        CPUHP_AP_PERF_X86_STARTING,
        CPUHP_AP_PERF_X86_AMD_IBS_STARTING,
        CPUHP_AP_PERF_X86_CQM_STARTING,
+       CPUHP_AP_PERF_X86_CSTATE_STARTING,
        CPUHP_AP_NOTIFY_STARTING,
        CPUHP_AP_ONLINE,
        CPUHP_TEARDOWN_CPU,
@@ -38,6 +39,7 @@ enum cpuhp_state {
        CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
        CPUHP_AP_PERF_X86_RAPL_ONLINE,
        CPUHP_AP_PERF_X86_CQM_ONLINE,
+       CPUHP_AP_PERF_X86_CSTATE_ONLINE,
        CPUHP_AP_NOTIFY_ONLINE,
        CPUHP_AP_ONLINE_DYN,
        CPUHP_AP_ONLINE_DYN_END         = CPUHP_AP_ONLINE_DYN + 30,
-- 
2.8.1