Try to debug Windows infinite loops in nanobench.

bench/nanobench.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <ctype.h>
 
 #include "Benchmark.h"
@@ skipping 32 matching lines @@
 DEFINE_string(config, "nonrendering 8888 gpu", "Configs to measure. Options: "
               "565 8888 gpu nonrendering debug nullgpu msaa4 msaa16 nvprmsaa4 nvprmsaa16 angle");
 DEFINE_double(gpuMs, 5, "Target bench time in millseconds for GPU.");
 DEFINE_int32(gpuFrameLag, 5, "Overestimate of maximum number of frames GPU allows to lag.");
 
 DEFINE_bool(cpu, true, "Master switch for CPU-bound work.");
 DEFINE_bool(gpu, true, "Master switch for GPU-bound work.");
 
 DEFINE_string(outResultsFile, "", "If given, write results here as JSON.");
 DEFINE_bool(resetGpuContext, true, "Reset the GrContext before running each bench.");
+DEFINE_int32(maxCalibrationAttempts, 3,
+             "Try up to this many times to guess loops for a bench, or skip the bench.");
 
 
 static SkString humanize(double ms) {
     if (ms > 1e+3) return SkStringPrintf("%.3gs",  ms/1e3);
     if (ms < 1e-3) return SkStringPrintf("%.3gns", ms*1e6);
 #ifdef SK_BUILD_FOR_WIN
     if (ms < 1)    return SkStringPrintf("%.3gus", ms*1e3);
 #else
     if (ms < 1)    return SkStringPrintf("%.3gµs", ms*1e3);
 #endif
@@ skipping 23 matching lines @@
     double overhead = 0;
     for (int i = 0; i < FLAGS_overheadLoops; i++) {
         overhead += time(1, NULL, NULL, NULL);
     }
     return overhead / FLAGS_overheadLoops;
 }
 
 static int cpu_bench(const double overhead, Benchmark* bench, SkCanvas* canvas, double* samples) {
     // First figure out approximately how many loops of bench it takes to make overhead negligible.
     double bench_plus_overhead;
+    int round = 0;
     do {
         bench_plus_overhead = time(1, bench, canvas, NULL);
-    } while (bench_plus_overhead < overhead);  // Shouldn't normally happen.
+        if (++round == FLAGS_maxCalibrationAttempts) {
+            // At some point we have to just give up.
+            return 0;
+        }
+    } while (bench_plus_overhead < overhead);
 
     // Later we'll just start and stop the timer once but loop N times.
     // We'll pick N to make timer overhead negligible:
     //
     //          overhead
     //  -------------------------  < FLAGS_overheadGoal
     //  overhead + N * Bench Time
     //
     // where bench_plus_overhead ≈ overhead + Bench Time.
     //
@@ skipping 190 matching lines @@
             continue;
         }
         log.bench(bench->getName(), bench->getSize().fX, bench->getSize().fY);
 
         SkTDArray<Target*> targets;
         create_targets(bench.get(), &targets);
 
         bench->preDraw();
         for (int j = 0; j < targets.count(); j++) {
             SkCanvas* canvas = targets[j]->surface.get() ? targets[j]->surface->getCanvas() : NULL;
+            const char* config = targets[j]->config;
 
             const int loops =
 #if SK_SUPPORT_GPU
                 Benchmark::kGPU_Backend == targets[j]->backend
                 ? gpu_bench(targets[j]->gl, bench.get(), canvas, samples.get())
                 :
 #endif
                  cpu_bench(       overhead, bench.get(), canvas, samples.get());
 
+            if (loops == 0) {
+                SkDebugf("Unable to time %s\t%s (overhead %s)\n",
+                         bench->getName(), config, humanize(overhead).c_str());
+                continue;
+            }
+
             Stats stats(samples.get(), FLAGS_samples);
-
-            const char* config = targets[j]->config;
-
             log.config(config);
             log.timer("min_ms",    stats.min);
             log.timer("median_ms", stats.median);
             log.timer("mean_ms",   stats.mean);
             log.timer("max_ms",    stats.max);
             log.timer("stddev_ms", sqrt(stats.var));
 
             if (FLAGS_runOnce) {
                 if (targets.count() == 1) {
                     config = ""; // Only print the config if we run the same bench on more than one.
@@ skipping 34 matching lines @@
     }
 
     return 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif