Fix event profiler segfault (#322)

Summary:
Pull Request resolved: #322

The change to lazy initialization of the ConfigLoader exposed an issue in the EventProfiler where a nullptr on demand configuration is dereferenced.

On-demand configuration should only be accessed if the profiler is actually actively handling an on-demand request.

Reviewed By: leitian

Differential Revision: D29378839

fbshipit-source-id: dbccdc78268e0d87002b369b463fd42082b2be37

Author: gdankel

libkineto/src/EventProfiler.cpp

@@ -590,7 +590,6 @@ void EventProfiler::dispatchSamples(
 }
 
 void EventProfiler::configure(Config& config, Config* onDemandConfig) {
-  LOG(INFO) << "configure";
   if (!sets_.empty()) {
     sets_[curEnabledSet_].setEnabled(false);
     clearSamples();

libkineto/src/EventProfilerController.cpp

@@ -351,7 +351,9 @@ void EventProfilerController::profilerLoop() {
       now = system_clock::now();
       next_sample_time = now + profiler_->samplePeriod();
       next_report_time = now + profiler_->reportPeriod();
-      next_on_demand_report_time = now + profiler_->onDemandReportPeriod();
+      if (profiler_->isOnDemandActive()) {
+        next_on_demand_report_time = now + profiler_->onDemandReportPeriod();
+      }
       next_multiplex_time = now + profiler_->multiplexPeriod();
       // Collect an initial sample and throw it away
       // The next sample is the first valid one
@@ -386,7 +388,7 @@ void EventProfilerController::profilerLoop() {
       profiler_->reportSamples();
       next_report_time += profiler_->reportPeriod();
     }
-    if (on_demand_report_count && now > next_on_demand_report_time) {
+    if (profiler_->isOnDemandActive() && now > next_on_demand_report_time) {
       VLOG(1) << "OnDemand Report #" << on_demand_report_count++;
       profiler_->reportOnDemandSamples();
       next_on_demand_report_time += profiler_->onDemandReportPeriod();