Move the calls to DumpSystemStats to a MayBlock thread.

Bug: 895309
Change-Id: Ib777900ba581c77e4e94d998cd36b3ca2ada9ba6
Reviewed-on: https://chromium-review.googlesource.com/c/1282393Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603743}

base/process/process_metrics_win.cc

@@ -18,6 +18,7 @@
 #include "base/process/memory.h"
 #include "base/process/process_metrics_iocounters.h"
 #include "base/sys_info.h"
+#include "base/threading/scoped_blocking_call.h"
 
 namespace base {
 namespace {
@@ -345,12 +346,15 @@ BASE_EXPORT bool GetSystemPerformanceInfo(SystemPerformanceInfo* info) {
     return false;
 
   SYSTEM_PERFORMANCE_INFORMATION counters = {};
-  const NTSTATUS status = query_system_information_ptr(
-      ::SystemPerformanceInformation, &counters,
-      sizeof(SYSTEM_PERFORMANCE_INFORMATION), nullptr);
-
-  if (status != STATUS_SUCCESS)
+  {
+    // The call to NtQuerySystemInformation might block on a lock.
+    base::ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
+    if (query_system_information_ptr(::SystemPerformanceInformation, &counters,
+                                     sizeof(SYSTEM_PERFORMANCE_INFORMATION),
+                                     nullptr) != STATUS_SUCCESS) {
       return false;
+    }
+  }
 
   info->idle_time = counters.IdleTime.QuadPart;
   info->read_transfer_count = counters.ReadTransferCount.QuadPart;

base/trace_event/trace_event_system_stats_monitor.cc

@@ -6,6 +6,7 @@
 
 #include <memory>
 
+#include "base/bind.h"
 #include "base/debug/leak_annotations.h"
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
@@ -14,6 +15,7 @@
 #include "base/process/process_metrics.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
+#include "base/task/post_task.h"
 #include "base/threading/thread_local_storage.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
@@ -49,6 +51,17 @@ void SystemStatsHolder::GetSystemProfilingStats() {
   system_stats_ = SystemMetrics::Sample();
 }
 
+void DumpSystemStatsImpl(TraceEventSystemStatsMonitor* stats_monitor) {
+  std::unique_ptr<SystemStatsHolder> dump_holder =
+      std::make_unique<SystemStatsHolder>();
+  dump_holder->GetSystemProfilingStats();
+
+  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
+      TRACE_DISABLED_BY_DEFAULT("system_stats"),
+      "base::TraceEventSystemStatsMonitor::SystemStats", stats_monitor,
+      std::move(dump_holder));
+}
+
 }  // namespace
 
 //////////////////////////////////////////////////////////////////////////////
@@ -102,15 +115,17 @@ void TraceEventSystemStatsMonitor::StartProfiling() {
                                weak_factory_.GetWeakPtr()));
 }
 
-// If system tracing is enabled, dumps a profile to the tracing system.
 void TraceEventSystemStatsMonitor::DumpSystemStats() {
-  std::unique_ptr<SystemStatsHolder> dump_holder(new SystemStatsHolder());
-  dump_holder->GetSystemProfilingStats();
-
-  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("system_stats"),
-      "base::TraceEventSystemStatsMonitor::SystemStats", this,
-      std::move(dump_holder));
+  // Calls to |DumpSystemStatsImpl| might be blocking.
+  //
+  // TODO(sebmarchand): Ideally the timer that calls this function should use a
+  // thread with the MayBlock trait to avoid having to use a trampoline here.
+  // This isn't currently possible due to https://crbug.com/896990.
+  base::PostTaskWithTraits(
+      FROM_HERE,
+      {base::MayBlock(), base::TaskPriority::BEST_EFFORT,
+       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN},
+      base::BindOnce(&DumpSystemStatsImpl, base::Unretained(this)));
 }
 
 void TraceEventSystemStatsMonitor::StopProfiling() {