Bug 718629 - intermittent waitpid failure causes OpenGL features to be blacklisted on X11 - r=karlt

toolkit/xre/glxtest.cpp

@@ -231,15 +231,6 @@ static void glxtest()
   if (length >= bufsize)
     fatal_error("GL strings length too large for buffer size");
 
-  ///// Check that no X error happened /////
-  // In case of X errors, our X error handler will exit() now.
-  // We really want to make sure that the system is able to create a GL context without generating X errors,
-  // as these would crash the application.
-  XSync(dpy, False);
-  
-  ///// Finally write data to the pipe /////
-  write(write_end_of_the_pipe, buf, length);
-
   ///// Clean up. Indeed, the parent process might fail to kill us (e.g. if it doesn't need to check GL info)
   ///// so we might be staying alive for longer than expected, so it's important to consume as little memory as
   ///// possible. Also we want to check that we're able to do that too without generating X errors.
@@ -249,6 +240,9 @@ static void glxtest()
   XFreePixmap(dpy, pixmap);
   XCloseDisplay(dpy);
   dlclose(libgl);
+
+  ///// Finally write data to the pipe
+  write(write_end_of_the_pipe, buf, length);
 }
 
 /** \returns true in the child glxtest process, false in the parent process */

widget/xpwidgets/GfxInfoX11.cpp

@@ -93,7 +93,8 @@ GfxInfo::GetData()
     close(glxtest_pipe);
     glxtest_pipe = 0;
 
-    // bytesread < 0 would mean that the above read() call failed. This should never happen.
+    // bytesread < 0 would mean that the above read() call failed.
+    // This should never happen. If it did, the outcome would be to blacklist anyway.
     if (bytesread < 0)
         bytesread = 0;
 
@@ -111,10 +112,15 @@ GfxInfo::GetData()
         wait_for_glxtest_process = false;
         if (waitpid(glxtest_pid, &glxtest_status, 0) == -1) {
             waitpid_errno = errno;
-            if (waitpid_errno == EINTR)
+            if (waitpid_errno == EINTR) {
                 wait_for_glxtest_process = true;
-            else
-                waiting_for_glxtest_process_failed = true;
+            } else {
+                // Bug 718629
+                // ECHILD happens when the glxtest process got reaped got reaped after a PR_CreateProcess
+                // as per bug 227246. This shouldn't matter, as we still seem to get the data
+                // from the pipe, and if we didn't, the outcome would be to blacklist anyway.
+                waiting_for_glxtest_process_failed = (waitpid_errno != ECHILD);
+            }
         }
     }