perf, x86: Avoid double disable on throttle vs ioctl(PERF_IOC_DISABLE)

Calling ioctl(PERF_EVENT_IOC_DISABLE) on a thottled counter would result
in a double disable, cure this by using x86_pmu_{start,stop} for
throttle/unthrottle and teach x86_pmu_stop() to check ->active_mask.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event_intel_ds.c

@@ -461,7 +461,6 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
 }
 
 static int intel_pmu_save_and_restart(struct perf_event *event);
-static void intel_pmu_disable_event(struct perf_event *event);
 
 static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
 {
@@ -528,7 +527,7 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
 		regs.flags &= ~PERF_EFLAGS_EXACT;
 
 	if (perf_event_overflow(event, 1, &data, &regs))
-		intel_pmu_disable_event(event);
+		x86_pmu_stop(event);
 
 out:
 	intel_pmu_pebs_enable_all();
@@ -603,7 +602,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
 			regs.flags &= ~PERF_EFLAGS_EXACT;
 
 		if (perf_event_overflow(event, 1, &data, &regs))
-			intel_pmu_disable_event(event);
+			x86_pmu_stop(event);
 	}
 out:
 	intel_pmu_pebs_enable_all();