perf, x86: Fix AMD hotplug & constraint initialization

Commit 3f6da39 ("perf: Rework and fix the arch CPU-hotplug hooks") moved
the amd northbridge allocation from CPUS_ONLINE to CPUS_PREPARE_UP
however amd_nb_id() doesn't work yet on prepare so it would simply bail
basically reverting to a state where we do not properly track node wide
constraints - causing weird perf results.

Fix up the AMD NorthBridge initialization code by allocating from
CPU_UP_PREPARE and installing it from CPU_STARTING once we have the
proper nb_id. It also properly deals with the allocation failing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ robustify using amd_has_nb() ]
Signed-off-by: Stephane Eranian <eranian@google.com>
LKML-Reference: <1269353485.5109.48.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 5fb490c..bd28cf9 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -158,7 +158,7 @@ struct x86_pmu {
                                                 struct perf_event *event);
        struct event_constraint *event_constraints;
 
-       void            (*cpu_prepare)(int cpu);
+       int             (*cpu_prepare)(int cpu);
        void            (*cpu_starting)(int cpu);
        void            (*cpu_dying)(int cpu);
        void            (*cpu_dead)(int cpu);
@@ -1333,11 +1333,12 @@ static int __cpuinit
 x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
 {
        unsigned int cpu = (long)hcpu;
+       int ret = NOTIFY_OK;
 
        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_UP_PREPARE:
                if (x86_pmu.cpu_prepare)
-                       x86_pmu.cpu_prepare(cpu);
+                       ret = x86_pmu.cpu_prepare(cpu);
                break;
 
        case CPU_STARTING:
@@ -1350,6 +1351,7 @@ x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
                        x86_pmu.cpu_dying(cpu);
                break;
 
+       case CPU_UP_CANCELED:
        case CPU_DEAD:
                if (x86_pmu.cpu_dead)
                        x86_pmu.cpu_dead(cpu);
@@ -1359,7 +1361,7 @@ x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
                break;
        }
 
-       return NOTIFY_OK;
+       return ret;
 }
 
 static void __init pmu_check_apic(void)

diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index b87e0b6..db6f7d4 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -137,6 +137,13 @@ static inline int amd_is_nb_event(struct hw_perf_event *hwc)
        return (hwc->config & 0xe0) == 0xe0;
 }
 
+static inline int amd_has_nb(struct cpu_hw_events *cpuc)
+{
+       struct amd_nb *nb = cpuc->amd_nb;
+
+       return nb && nb->nb_id != -1;
+}
+
 static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
                                      struct perf_event *event)
 {
@@ -147,7 +154,7 @@ static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
        /*
         * only care about NB events
         */
-       if (!(nb && amd_is_nb_event(hwc)))
+       if (!(amd_has_nb(cpuc) && amd_is_nb_event(hwc)))
                return;
 
        /*
@@ -214,7 +221,7 @@ amd_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
        /*
         * if not NB event or no NB, then no constraints
         */
-       if (!(nb && amd_is_nb_event(hwc)))
+       if (!(amd_has_nb(cpuc) && amd_is_nb_event(hwc)))
                return &unconstrained;
 
        /*
@@ -293,51 +300,55 @@ static struct amd_nb *amd_alloc_nb(int cpu, int nb_id)
        return nb;
 }
 
-static void amd_pmu_cpu_online(int cpu)
+static int amd_pmu_cpu_prepare(int cpu)
+{
+       struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+
+       WARN_ON_ONCE(cpuc->amd_nb);
+
+       if (boot_cpu_data.x86_max_cores < 2)
+               return NOTIFY_OK;
+
+       cpuc->amd_nb = amd_alloc_nb(cpu, -1);
+       if (!cpuc->amd_nb)
+               return NOTIFY_BAD;
+
+       return NOTIFY_OK;
+}
+
+static void amd_pmu_cpu_starting(int cpu)
 {
-       struct cpu_hw_events *cpu1, *cpu2;
-       struct amd_nb *nb = NULL;
+       struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
+       struct amd_nb *nb;
        int i, nb_id;
 
        if (boot_cpu_data.x86_max_cores < 2)
                return;
 
-       /*
-        * function may be called too early in the
-        * boot process, in which case nb_id is bogus
-        */
        nb_id = amd_get_nb_id(cpu);
-       if (nb_id == BAD_APICID)
-               return;
-
-       cpu1 = &per_cpu(cpu_hw_events, cpu);
-       cpu1->amd_nb = NULL;
+       WARN_ON_ONCE(nb_id == BAD_APICID);
 
        raw_spin_lock(&amd_nb_lock);
 
        for_each_online_cpu(i) {
-               cpu2 = &per_cpu(cpu_hw_events, i);
-               nb = cpu2->amd_nb;
-               if (!nb)
+               nb = per_cpu(cpu_hw_events, i).amd_nb;
+               if (WARN_ON_ONCE(!nb))
                        continue;
-               if (nb->nb_id == nb_id)
-                       goto found;
-       }
 
-       nb = amd_alloc_nb(cpu, nb_id);
-       if (!nb) {
-               pr_err("perf_events: failed NB allocation for CPU%d\n", cpu);
-               raw_spin_unlock(&amd_nb_lock);
-               return;
+               if (nb->nb_id == nb_id) {
+                       kfree(cpuc->amd_nb);
+                       cpuc->amd_nb = nb;
+                       break;
+               }
        }
-found:
-       nb->refcnt++;
-       cpu1->amd_nb = nb;
+
+       cpuc->amd_nb->nb_id = nb_id;
+       cpuc->amd_nb->refcnt++;
 
        raw_spin_unlock(&amd_nb_lock);
 }
 
-static void amd_pmu_cpu_offline(int cpu)
+static void amd_pmu_cpu_dead(int cpu)
 {
        struct cpu_hw_events *cpuhw;
 
@@ -349,8 +360,10 @@ static void amd_pmu_cpu_offline(int cpu)
        raw_spin_lock(&amd_nb_lock);
 
        if (cpuhw->amd_nb) {
-               if (--cpuhw->amd_nb->refcnt == 0)
-                       kfree(cpuhw->amd_nb);
+               struct amd_nb *nb = cpuhw->amd_nb;
+
+               if (nb->nb_id == -1 || --nb->refcnt == 0)
+                       kfree(nb);
 
                cpuhw->amd_nb = NULL;
        }
@@ -379,8 +392,9 @@ static __initconst struct x86_pmu amd_pmu = {
        .get_event_constraints  = amd_get_event_constraints,
        .put_event_constraints  = amd_put_event_constraints,
 
-       .cpu_prepare            = amd_pmu_cpu_online,
-       .cpu_dead               = amd_pmu_cpu_offline,
+       .cpu_prepare            = amd_pmu_cpu_prepare,
+       .cpu_starting           = amd_pmu_cpu_starting,
+       .cpu_dead               = amd_pmu_cpu_dead,
 };
 
 static __init int amd_pmu_init(void)