Bug 1240985 - IPC glib deadlock fix (r=jld)

ipc/chromium/src/base/message_pump_glib.cc

@@ -124,7 +124,8 @@ namespace base {
 MessagePumpForUI::MessagePumpForUI()
     : state_(NULL),
       context_(g_main_context_default()),
-      wakeup_gpollfd_(new GPollFD) {
+      wakeup_gpollfd_(new GPollFD),
+      pipe_full_(false) {
   // Create our wakeup pipe, which is used to flag when work was scheduled.
   int fds[2];
   CHECK(pipe(fds) == 0);
@@ -230,10 +231,12 @@ bool MessagePumpForUI::HandleCheck() {
   if (!state_)  // state_ may be null during tests.
     return false;
 
-  // We should only ever have a single message on the wakeup pipe, since we
-  // are only signaled when the queue went from empty to non-empty.  The glib
-  // poll will tell us whether there was data, so this read shouldn't block.
+  // We should only ever have a single message on the wakeup pipe since we only
+  // write to the pipe when pipe_full_ is false. The glib poll will tell us
+  // whether there was data, so this read shouldn't block.
   if (wakeup_gpollfd_->revents & G_IO_IN) {
+    pipe_full_ = false;
+
     char msg;
     if (HANDLE_EINTR(read(wakeup_pipe_read_, &msg, 1)) != 1 || msg != '!') {
       NOTREACHED() << "Error reading from the wakeup pipe.";
@@ -297,6 +300,11 @@ void MessagePumpForUI::Quit() {
 }
 
 void MessagePumpForUI::ScheduleWork() {
+  bool was_full = pipe_full_.exchange(true);
+  if (was_full) {
+    return;
+  }
+
   // This can be called on any thread, so we don't want to touch any state
   // variables as we would then need locks all over.  This ensures that if
   // we are sleeping in a poll that we will wake up.

ipc/chromium/src/base/message_pump_glib.h

@@ -9,6 +9,7 @@
 #include "base/observer_list.h"
 #include "base/time.h"
 #include "mozilla/UniquePtr.h"
+#include "mozilla/Atomics.h"
 
 typedef union _GdkEvent GdkEvent;
 typedef struct _GMainContext GMainContext;
@@ -131,6 +132,8 @@ class MessagePumpForUI : public MessagePump {
   // Use an autoptr to avoid needing the definition of GPollFD in the header.
   mozilla::UniquePtr<GPollFD> wakeup_gpollfd_;
 
+  mozilla::Atomic<bool> pipe_full_;
+
   // List of observers.
   ObserverList<Observer> observers_;