Track thread activities in order to diagnose hangs.

base/synchronization/waitable_event_win.cc

Index: base/synchronization/waitable_event_win.cc
diff --git a/base/synchronization/waitable_event_win.cc b/base/synchronization/waitable_event_win.cc
index 89ace19961a7e7e42bca88e2f0a3663a2e30e763..50d38c4c741a1d7acb017b640b4fd1f84ffaba01 100644
--- a/base/synchronization/waitable_event_win.cc
+++ b/base/synchronization/waitable_event_win.cc
@@ -9,6 +9,7 @@
 
 #include <utility>
 
+#include "base/debug/activity_tracker.h"
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/threading/thread_restrictions.h"
@@ -45,6 +46,7 @@ bool WaitableEvent::IsSignaled() {
 
 void WaitableEvent::Wait() {
   base::ThreadRestrictions::AssertWaitAllowed();
+  base::debug::ScopedEventActivity event_activity(this);
   DWORD result = WaitForSingleObject(handle_.Get(), INFINITE);
   // It is most unexpected that this should ever fail.  Help consumers learn
   // about it if it should ever fail.
@@ -53,6 +55,7 @@ void WaitableEvent::Wait() {
 
 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
   base::ThreadRestrictions::AssertWaitAllowed();
+  base::debug::ScopedEventActivity event_activity(this);
   DCHECK_GE(max_time, TimeDelta());
   // Truncate the timeout to milliseconds. The API specifies that this method
   // can return in less than |max_time| (when returning false), as the argument
@@ -75,6 +78,7 @@ bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
 // static
 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
   base::ThreadRestrictions::AssertWaitAllowed();
+  base::debug::ScopedEventActivity event_activity(events[0]);

[manzagop (departed), 2016/06/01 21:59:41]

A comment for this?

[bcwhite, 2016/06/02 16:18:16]

Done.

   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
   CHECK_LE(count, static_cast<size_t>(MAXIMUM_WAIT_OBJECTS))
       << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";