perf, amd: Remove the nb lock

Since all the hotplug stuff is serialized by the hotplug mutex,
do away with the amd_nb_lock.

Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event_amd.c

@@ -1,7 +1,5 @@
 #ifdef CONFIG_CPU_SUP_AMD
 
-static DEFINE_RAW_SPINLOCK(amd_nb_lock);
-
 static __initconst const u64 amd_hw_cache_event_ids
 				[PERF_COUNT_HW_CACHE_MAX]
 				[PERF_COUNT_HW_CACHE_OP_MAX]
@@ -275,7 +273,7 @@ done:
 	return &emptyconstraint;
 }
 
-static struct amd_nb *amd_alloc_nb(int cpu, int nb_id)
+static struct amd_nb *amd_alloc_nb(int cpu)
 {
 	struct amd_nb *nb;
 	int i;
@@ -285,7 +283,7 @@ static struct amd_nb *amd_alloc_nb(int cpu, int nb_id)
 	if (!nb)
 		return NULL;
 
-	nb->nb_id = nb_id;
+	nb->nb_id = -1;
 
 	/*
 	 * initialize all possible NB constraints
@@ -306,7 +304,7 @@ static int amd_pmu_cpu_prepare(int cpu)
 	if (boot_cpu_data.x86_max_cores < 2)
 		return NOTIFY_OK;
 
-	cpuc->amd_nb = amd_alloc_nb(cpu, -1);
+	cpuc->amd_nb = amd_alloc_nb(cpu);
 	if (!cpuc->amd_nb)
 		return NOTIFY_BAD;
 
@@ -325,8 +323,6 @@ static void amd_pmu_cpu_starting(int cpu)
 	nb_id = amd_get_nb_id(cpu);
 	WARN_ON_ONCE(nb_id == BAD_APICID);
 
-	raw_spin_lock(&amd_nb_lock);
-
 	for_each_online_cpu(i) {
 		nb = per_cpu(cpu_hw_events, i).amd_nb;
 		if (WARN_ON_ONCE(!nb))
@@ -341,8 +337,6 @@ static void amd_pmu_cpu_starting(int cpu)
 
 	cpuc->amd_nb->nb_id = nb_id;
 	cpuc->amd_nb->refcnt++;
-
-	raw_spin_unlock(&amd_nb_lock);
 }
 
 static void amd_pmu_cpu_dead(int cpu)
@@ -354,8 +348,6 @@ static void amd_pmu_cpu_dead(int cpu)
 
 	cpuhw = &per_cpu(cpu_hw_events, cpu);
 
-	raw_spin_lock(&amd_nb_lock);
-
 	if (cpuhw->amd_nb) {
 		struct amd_nb *nb = cpuhw->amd_nb;
 
@@ -364,8 +356,6 @@ static void amd_pmu_cpu_dead(int cpu)
 
 		cpuhw->amd_nb = NULL;
 	}
-
-	raw_spin_unlock(&amd_nb_lock);
 }
 
 static __initconst const struct x86_pmu amd_pmu = {