arm/perf: Fix hotplug state machine conversion

Mark Rutland pointed out that this commit is incomplete:

  7d88eb695a1f ("arm/perf: Convert to hotplug state machine")

The problem is that:

 > We may have multiple PMUs (e.g. two in big.LITTLE systems), and
 > __oprofile_cpu_pmu only contains one of these. So this conversion is not
 > correct.
 >
 > We were relying on the notifier list implicitly containing a list of
 > those PMUs. It seems like we need an explicit list here.
 >
 > We keep __oprofile_cpu_pmu around for legacy 32-bit users of OProfile
 > (on non-hetereogeneous systems), and that's all that the variable should
 > be used for.

Introduce arm_pmu_list to correctly handle multiple PMUs in the system.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-tip-commits@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160719111733.GA22911@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index ae9fc6c6add35b8cff3d0c5523e89b8275d64204..f6ab4f7f75bf97973227023e6d6933c6ca46ad98 100644 (file)
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -685,6 +685,9 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
        return 0;
 }
 
+static DEFINE_MUTEX(arm_pmu_mutex);
+static LIST_HEAD(arm_pmu_list);
+
 /*
  * PMU hardware loses all context when a CPU goes offline.
  * When a CPU is hotplugged back in, since some hardware registers are
@@ -693,12 +696,17 @@ static int cpu_pmu_request_irq(struct arm_pmu *cpu_pmu, irq_handler_t handler)
  */
 static int arm_perf_starting_cpu(unsigned int cpu)
 {
-       if (!__oprofile_cpu_pmu)
-               return 0;
-       if (!cpumask_test_cpu(cpu, &__oprofile_cpu_pmu->supported_cpus))
-               return 0;
-       if (__oprofile_cpu_pmu->reset)
-               __oprofile_cpu_pmu->reset(__oprofile_cpu_pmu);
+       struct arm_pmu *pmu;
+
+       mutex_lock(&arm_pmu_mutex);
+       list_for_each_entry(pmu, &arm_pmu_list, entry) {
+
+               if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
+                       continue;
+               if (pmu->reset)
+                       pmu->reset(pmu);
+       }
+       mutex_unlock(&arm_pmu_mutex);
        return 0;
 }
 
@@ -810,11 +818,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
        if (!cpu_hw_events)
                return -ENOMEM;
 
-       err = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_STARTING,
-                                       "AP_PERF_ARM_STARTING",
-                                       arm_perf_starting_cpu, NULL);
-       if (err)
-               goto out_hw_events;
+       mutex_lock(&arm_pmu_mutex);
+       list_add_tail(&cpu_pmu->entry, &arm_pmu_list);
+       mutex_unlock(&arm_pmu_mutex);
 
        err = cpu_pm_pmu_register(cpu_pmu);
        if (err)
@@ -850,8 +856,9 @@ static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
        return 0;
 
 out_unregister:
-       cpuhp_remove_state_nocalls(CPUHP_AP_PERF_ARM_STARTING);
-out_hw_events:
+       mutex_lock(&arm_pmu_mutex);
+       list_del(&cpu_pmu->entry);
+       mutex_unlock(&arm_pmu_mutex);
        free_percpu(cpu_hw_events);
        return err;
 }
@@ -859,7 +866,9 @@ out_hw_events:
 static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)
 {
        cpu_pm_pmu_unregister(cpu_pmu);
-       cpuhp_remove_state_nocalls(CPUHP_AP_PERF_ARM_STARTING);
+       mutex_lock(&arm_pmu_mutex);
+       list_del(&cpu_pmu->entry);
+       mutex_unlock(&arm_pmu_mutex);
        free_percpu(cpu_pmu->hw_events);
 }
 
@@ -1019,8 +1028,6 @@ int arm_pmu_device_probe(struct platform_device *pdev,
        if (ret)
                goto out_destroy;
 
-       WARN(__oprofile_cpu_pmu, "%s(): missing PMU strucure for CPU-hotplug\n",
-            __func__);
        if (!__oprofile_cpu_pmu)
                __oprofile_cpu_pmu = pmu;
 
@@ -1038,3 +1045,17 @@ out_free:
        kfree(pmu);
        return ret;
 }
+
+static int arm_pmu_hp_init(void)
+{
+       int ret;
+
+       ret = cpuhp_setup_state_nocalls(CPUHP_AP_PERF_ARM_STARTING,
+                                       "AP_PERF_ARM_STARTING",
+                                       arm_perf_starting_cpu, NULL);
+       if (ret)
+               pr_err("CPU hotplug notifier for ARM PMU could not be registered: %d\n",
+                      ret);
+       return ret;
+}
+subsys_initcall(arm_pmu_hp_init);

diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index e6ed34eb2b2b56ac2e1ac61a32005152228faa68..e18843809eec0f598018919e002dfb8dee58360d 100644 (file)
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -109,6 +109,7 @@ struct arm_pmu {
        DECLARE_BITMAP(pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
        struct platform_device  *plat_device;
        struct pmu_hw_events    __percpu *hw_events;
+       struct list_head        entry;
        struct notifier_block   cpu_pm_nb;
 };