Added code for renderer to cleanly exit.

content/renderer/renderer_main.cc

Index: content/renderer/renderer_main.cc
diff --git a/content/renderer/renderer_main.cc b/content/renderer/renderer_main.cc
index 306dee9aaf0ea6a511c53ae66884e431dc7abb29..c6e99e3cbb3060bb2e0c8be57b800e783aa07d2e 100644
--- a/content/renderer/renderer_main.cc
+++ b/content/renderer/renderer_main.cc
@@ -126,6 +126,31 @@ class RendererMessageLoopObserver : public MessageLoop::TaskObserver {
   DISALLOW_COPY_AND_ASSIGN(RendererMessageLoopObserver);
 };
 
+#if defined(RENDERER_CLEAN_EXIT)
+static void SigtermHandler(int signal_number)
+{
+  fprintf(stderr, "SIGTERM caught by the renderer process.\n");
+  fprintf(stderr, "Calling clean_exit().\n");

[Markus (顧孟勤), 2012/03/28 23:07:56]

You cannot call fprintf() from a signal handler.

[asharif1, 2012/03/29 02:13:11]

Done.

+  base::clean_exit(signal_number);
+}
+
+static void AddSigtermHandler()
+{
+  struct sigaction term_action;

[Markus (顧孟勤), 2012/03/28 23:07:56]

It is good practice to use memset() to clear out any data structure of type
"struct sigaction". If you do that, you also don't have to explicitly set
sa_flags.

[asharif1, 2012/03/29 02:13:11]

Done.

+  int return_value;
+  term_action.sa_handler = SigtermHandler;
+  sigfillset(&term_action.sa_mask);
+  term_action.sa_flags = 0;
+  fprintf(stderr, "Installing SIGTERM handler to the renderer process.\n");

[Markus (顧孟勤), 2012/03/28 23:07:56]

Why do you need to print this message? We typically don't print messages that
just inform about the normal execution of the program.

[asharif1, 2012/03/29 02:13:11]

Done.

+  return_value = sigaction(SIGTERM, &term_action, NULL);

[Markus (顧孟勤), 2012/03/28 23:07:56]

If sigaction() failed, you should trigger a CHECK() failure. Something is
clearly very wrong. If it didn't fail, then no need to print anything.

[asharif1, 2012/03/29 02:13:11]

Done.

+  if (!return_value)
+    fprintf(stderr, "Installed SIGTERM handler to the renderer process.\n");
+  else
+    fprintf(stderr,
+            "Couldn't install SIGTERM handler to the renderer process.\n");
+}
+#endif // defined(RENDERER_CLEAN_EXIT)
+
 // mainline routine for running as the Renderer process
 int RendererMain(const content::MainFunctionParams& parameters) {
   TRACE_EVENT_BEGIN_ETW("RendererMain", 0, "");
@@ -232,6 +257,10 @@ int RendererMain(const content::MainFunctionParams& parameters) {
 
     startup_timer.Stop();  // End of Startup Time Measurement.
 
+#if defined(RENDERER_CLEAN_EXIT)
+    AddSigtermHandler();

[Markus (顧孟勤), 2012/03/28 23:07:56]

Can you say a little more about the rationale for why we are adding this
handler?

The default behavior for this SIGTERM is to terminate the program. You can check
this by reading "man 7 signal". The only thing that your signal handler does
different is printing a message and (unreliably) running at_exit() handlers.

Is that what you need to do? If so, we should probably do things correctly. In
other words, we would need to find a way that the signal handler can safely
inform the main loop that it should exit.

And if we do that, then we probably should do so unconditionally. So, no need
for RENDERER_CLEAN_EXIT.

[asharif1, 2012/03/29 02:13:11]

Read the CL description.

My goal is to run exit handlers upon exit. That's it.

I experimented with just adding a signal handler here and calling exit() and
just calling exit() instead of _exit in the other file. Both need to be in place
for it to work.

Since you're more familiar with the codebase, what do you suggest I do to make
it cleanly exit instead of the current situation where both an uncaught SIGTERM
and _exit() call try to terminate the process around the same time.

+#endif
+
     if (run_loop) {
 #if defined(OS_MACOSX)
       if (pool)