sparc64: Fix pcr_ops initialization and usage bugs.

Christopher reports that perf_event_print_debug() can crash in uniprocessor
builds.  The crash is due to pcr_ops being NULL.

This happens because pcr_arch_init() is only invoked by smp_cpus_done() which
only executes in SMP builds.

init_hw_perf_events() is closely intertwined with pcr_ops being setup properly,
therefore:

1) Call pcr_arch_init() early on from init_hw_perf_events(), instead of
   from smp_cpus_done().

2) Do not hook up a PMU type if pcr_ops is NULL after pcr_arch_init().

3) Move init_hw_perf_events to a later initcall so that it we will be
   sure to invoke pcr_arch_init() after all cpus are brought up.

Finally, guard the one naked sequence of pcr_ops dereferences in
__global_pmu_self() with an appropriate NULL check.

Reported-by: Christopher Alexander Tobias Schulze <cat.schulze@alice-dsl.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 027e09986194..0be7bf978cb1 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -312,6 +312,9 @@ static void __global_pmu_self(int this_cpu)
 	struct global_pmu_snapshot *pp;
 	int i, num;
 
+	if (!pcr_ops)
+		return;
+
 	pp = &global_cpu_snapshot[this_cpu].pmu;
 
 	num = 1;