[Mac] Move the reset of signal handlers to be very soon after the fork, befor...

base/process_util_posix.cc

Index: base/process_util_posix.cc
===================================================================
--- base/process_util_posix.cc	(revision 58482)
+++ base/process_util_posix.cc	(working copy)
@@ -109,6 +109,15 @@
   _exit(1);
 }
 
+void ResetChildSignalHandlersToDefaults() {
+  // The previous signal handlers are likely to be meaningless in the child's
+  // context so we reset them to the defaults for now. http://crbug.com/44953
+  // These signal handlers are setup in browser_main.cc:BrowserMain
+  signal(SIGTERM, SIG_DFL);
+  signal(SIGHUP, SIG_DFL);
+  signal(SIGINT, SIG_DFL);
+}
+
 }  // anonymous namespace
 
 ProcessId GetCurrentProcId() {
@@ -323,6 +332,9 @@
     case -1:
       return pid;
     case 0: {  // child
+      // Must reset signal handlers before doing any mach IPC, as the mach IPC
+      // calls can potentially hang forever.
+      ResetChildSignalHandlersToDefaults();
       MachSendMessage child_message(/* id= */0);
       if (!child_message.AddDescriptor(mach_task_self())) {
         LOG(ERROR) << "child AddDescriptor(mach_task_self()) failed.";
@@ -529,12 +541,10 @@
     RestoreDefaultExceptionHandler();
 #endif
 
-    // The previous signal handlers are likely to be meaningless in the child's
-    // context so we reset them to the defaults for now. http://crbug.com/44953
-    // These signal handlers are setup in browser_main.cc:BrowserMain
-    signal(SIGTERM, SIG_DFL);
-    signal(SIGHUP, SIG_DFL);
-    signal(SIGINT, SIG_DFL);
+    // On mac, the signal handlers are reset in |fork_and_get_task()|.
+#if !defined(OS_MACOSX)
+    ResetChildSignalHandlersToDefaults();
+#endif
 
 #if 0
     // When debugging it can be helpful to check that we really aren't making