[Mac] Move the reset of signal handlers to be very soon after the fork, before we do any mach IPC.

The MachPortSender constructor can sometimes hang forever (gets stuck in bootstrap_look_up()), so it is important to reset the child's signal handlers as early as possible.

Nico would like me to mention that this was his idea.

This is take two.  I couldn't reproduce the unit_tests failures either locally or on the release try bots.

BUG=35374
TEST=If in the forever backwards spinner state, closing the tab should not quit the browser.
TEST=In general, renderers and extensions and plugins should still work.
Review URL: http://codereview.chromium.org/3302009

TBR=rohitrao@chromium.org
Review URL: http://codereview.chromium.org/3322013

TBR=rohitrao@chromium.org
Review URL: http://codereview.chromium.org/3360009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@58572 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 16 insertions, 6 deletions

diff --git a/base/process_util_posix.cc b/base/process_util_posix.cc
index d50ff9f..8fe64d0 100644
--- a/base/process_util_posix.cc
+++ b/base/process_util_posix.cc
@@ -109,6 +109,15 @@ void StackDumpSignalHandler(int signal) {
   _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 @@ static pid_t fork_and_get_task(task_t* child_task) {
     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 @@ bool LaunchApp(
     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