[Webkit-unassigned] [Bug 117499] [GTK] Issue performing a navigation action from DOM bindings

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=117499


Carlos Garcia Campos <cgarcia at igalia.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID




--- Comment #3 from Carlos Garcia Campos <cgarcia at igalia.com>  2013-06-20 00:09:54 PST ---
(In reply to comment #2)
> Checking the UIProcess backtrace it's clear that the problem is due a synchronous D-Bus call which causes that the UIProcess and it doesn't reply to the WebProcess when it's asked about the navigation policy.
> 
> UIProcess backtrace:
> 
> #0  0x00007f366a4f91bd in poll () at ../sysdeps/unix/syscall-template.S:81
> #1  0x00007f366b4514ec in g_main_context_poll (n_fds=1, fds=0xbfc9c0, timeout=25000, context=0xbfbf60, priority=<optimized out>) at gmain.c:3995
> #2  g_main_context_iterate (context=0xbfbf60, block=block at entry=1, dispatch=dispatch at entry=1, self=<optimized out>) at gmain.c:3696
> #3  0x00007f366b4519ca in g_main_loop_run (loop=0xbfc510) at gmain.c:3895
> #4  0x00007f366b63e1d3 in g_dbus_connection_send_message_with_reply_sync (connection=connection at entry=0xbb4410, message=message at entry=0xbfaad0, flags=flags at entry=G_DBUS_SEND_MESSAGE_FLAGS_NONE, 
>     timeout_msec=timeout_msec at entry=-1, out_serial=out_serial at entry=0x0, cancellable=cancellable at entry=0x0, error=error at entry=0x7fffe3a14098) at gdbusconnection.c:2240
> #5  0x00007f366b63e5e0 in g_dbus_connection_call_sync_internal (connection=0xbb4410, bus_name=bus_name at entry=0xbfc4f0 ":1.0", object_path=0xbf9e80 "/org/webkit/gtk/WebExtensionTest", 
>     interface_name=interface_name at entry=0xba6390 "org.webkit.gtk.WebExtensionTest", method_name=method_name at entry=0x407ab8 "GetTitle", parameters=parameters at entry=0x7f3604005a40, reply_type=0x7f366b67010f, 
>     flags=G_DBUS_CALL_FLAGS_NONE, timeout_msec=-1, fd_list=0x0, out_fd_list=0x0, cancellable=0x0, error=0x0) at gdbusconnection.c:5564
> #6  0x00007f366b640895 in g_dbus_connection_call_with_unix_fd_list_sync (connection=<optimized out>, bus_name=bus_name at entry=0xbfc4f0 ":1.0", object_path=<optimized out>, 
>     interface_name=interface_name at entry=0xba6390 "org.webkit.gtk.WebExtensionTest", method_name=method_name at entry=0x407ab8 "GetTitle", parameters=parameters at entry=0x7f3604005a40, reply_type=0x7f366b67010f, 
>     reply_type at entry=0x0, flags=flags at entry=G_DBUS_CALL_FLAGS_NONE, timeout_msec=timeout_msec at entry=-1, fd_list=fd_list at entry=0x0, out_fd_list=out_fd_list at entry=0x0, cancellable=cancellable at entry=0x0, 
>     error=error at entry=0x0) at gdbusconnection.c:5908
> #7  0x00007f366b649d25 in g_dbus_proxy_call_sync_internal (proxy=0xba7250, method_name=<optimized out>, parameters=0x7f3604005a40, flags=G_DBUS_CALL_FLAGS_NONE, timeout_msec=<optimized out>, 
>     fd_list=fd_list at entry=0x0, out_fd_list=out_fd_list at entry=0x0, cancellable=0x0, error=error at entry=0x0) at gdbusproxy.c:2910
> #8  0x00007f366b64bc43 in g_dbus_proxy_call_sync (proxy=<optimized out>, method_name=<optimized out>, parameters=<optimized out>, flags=<optimized out>, timeout_msec=<optimized out>, 
>     cancellable=<optimized out>, error=0x0) at gdbusproxy.c:3102
> #9  0x000000000040500b in testWebExtensionGetTitle(WebViewTest*, void const*) ()
> #10 0x00007f366b47407d in test_case_run (tc=0xb24390) at gtestutils.c:1714
> #11 g_test_run_suite_internal (suite=suite at entry=0xab70c0, path=<optimized out>, path at entry=0x7f366b4ba6ad "") at gtestutils.c:1767
> #12 0x00007f366b4741f6 in g_test_run_suite_internal (suite=suite at entry=0xb264c0, path=<optimized out>, path at entry=0x7f366b4ba6ad "") at gtestutils.c:1778
> #13 0x00007f366b4741f6 in g_test_run_suite_internal (suite=suite at entry=0xb264a0, path=<optimized out>, path at entry=0x7f366b4ba6ad "") at gtestutils.c:1778
> #14 0x00007f366b47455b in g_test_run_suite (suite=0xb264a0) at gtestutils.c:1823
> #15 0x0000000000405904 in main ()
> 
> 
> I've checked that this works properly if I use an async D-Bus call, so it's not a WK bug.
> 
> Anyway I'm wondering if we should add some documentation warning the users about this issue, explaining that if they use a WebKitWebExtension synchronously this kind of deadlock could happen while playing with the DOM bindings. What do you think?

I see, yes, so the problem is not the DOM code itself, but that it's called in a D-BUS sync message handler. D-BUS uses a nested main loop for sync messages in the caller, so if the web process tries to send a sync message to the UI process, both will be waiting forever. It's unfortunate because we can't know whether a DOM call can produce a sync communication between web and UI processes, but at least we can control the D-BUS messages that our extension uses. I'm not sure it's necessary to document it, any synchronous call is always discouraged, we use them in the unit tests, but not in production code. I'm going to close this as invalid, since it's not actually a WebKit bug.

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