[patch 16/20] perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode()

[Thomas Gleixner]

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

If intel_snb_check_microcode() is invoked via
  microcode_init -> perf_check_microcode -> intel_snb_check_microcode

then get_online_cpus() is invoked nested. This works with the current
implementation of get_online_cpus() but prevents converting it to a percpu
rwsem.

intel_snb_check_microcode() is also invoked from intel_sandybridge_quirk()
unprotected.

Drop get_online_cpus() from intel_snb_check_microcode() and add it to
intel_sandybridge_quirk() so both call sites are protected.

Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: x...@kernel.org

---
 arch/x86/events/intel/core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3389,12 +3389,10 @@ static void intel_snb_check_microcode(vo
        int pebs_broken = 0;
        int cpu;
 
-       get_online_cpus();
        for_each_online_cpu(cpu) {
                if ((pebs_broken = intel_snb_pebs_broken(cpu)))
                        break;
        }
-       put_online_cpus();
 
        if (pebs_broken == x86_pmu.pebs_broken)
                return;
@@ -3467,7 +3465,9 @@ static bool check_msr(unsigned long msr,
 static __init void intel_sandybridge_quirk(void)
 {
        x86_pmu.check_microcode = intel_snb_check_microcode;
+       get_online_cpus();
        intel_snb_check_microcode();
+       put_online_cpus();
 }
 
 static const struct { int id; char *name; } intel_arch_events_map[] 
__initconst = {