Re: libseed-list bug with threads and closures?

From: Jonatan Liljedahl <lijon kymatica com>
To: libseed-list gnome org
Subject: Re: libseed-list bug with threads and closures?
Date: Tue, 03 Aug 2010 21:12:25 +0200

Commenting out JSGlobalContextRelease ((JSGlobalContextRef) ctx) at theend of seed_handle_closure() in seed-closure.c makes the problem "goaway", but of course leaves the ctx in the land of forgotten pointers...

So, is the problem that the ctx is released before the thread exits, orthat it's release before any nested functions inside the thread finishes(like callbacks passed to idle_add or timeout_add), or both?

If I understand correctly, the ctx *should* be alive as long as thethread exists, since the ctx is created before the javascript threadfunction is called and released after it has returned. But! I still geta crash on JSGlobalContextRelease() with just a simple print() or "var x= 2*34" in the thread. (no nested callbacks involved)

Also, I guess this means that seed_handle_closure() is called from thethread and not from main? That brings the question, isseed_handle_closure() threadsafe?


/Jonatan


On 08/02/2010 03:15 PM, Jonatan Liljedahl wrote:

Any ideas on this? I'm stuck.. Hoping someone with more insight in
closures and gobject-introspection might help.

/Jonatan

On 07/28/2010 04:06 PM, Jonatan Liljedahl wrote:

This simple code crashes (output and stacktrace at the end of this
mail). I don't see why it shouldn't work. GLib.idle_add() is the
recommended way to defer stuff from a thread to the mainloop and I've
used it several times in C code.

Seems to be a problem with closures, threads and the garbage collector?

/////////// thread_bugs.js ////////////
var Gtk = imports.gi.Gtk;
Gtk.init(0,0);

var w = new Gtk.Window({border_width: 20});
var b = new Gtk.Button({label: "Foo"});
w.add(b);
w.show_all();

b.signal.clicked.connect(function() {
print("Clicked");
GLib.thread_create_full(function() {
print("Thread start");
var i=0;
var x=1.3;
for(i=0;i<9999999;i++) {
x *= 1.000004;
};
print(x);
print("Dispatch to mainloop");
GLib.idle_add(GLib.PRIORITY_DEFAULT_IDLE,function() {
print("In mainloop");
b.label = "Bar"+x;
return false;
});
},null,0,true);
});

Gtk.main();
//////////// EOF /////////////

Clicked

** (seed:2184): WARNING **: ArgumentError - probably due to incorrect
gir file (which may be fixed upstream) argument 2 must not be null for
function: thread_create_full

[New Thread 0xb57d8b70 (LWP 2188)]
Thread start
3.05975143636762e+17
Dispatch to mainloop
In mainloop

Program received signal SIGSEGV, Segmentation fault.
0x00cdbd12 in ?? () from /usr/lib/libwebkit-1.0.so.2
(gdb) bt
#0 0x00cdbd12 in ?? () from /usr/lib/libwebkit-1.0.so.2
#1 0x00cdc8a4 in ?? () from /usr/lib/libwebkit-1.0.so.2
#2 0x00cdc905 in ?? () from /usr/lib/libwebkit-1.0.so.2
#3 0x00cdd845 in ?? () from /usr/lib/libwebkit-1.0.so.2
#4 0x00cde4f0 in ?? () from /usr/lib/libwebkit-1.0.so.2
#5 0x00be63b3 in JSGlobalContextRelease () from
/usr/lib/libwebkit-1.0.so.2
#6 0x00137bb6 in seed_handle_closure (cif=0x81ccc00, result=0xbfffec38,
args=0xbfffebd0, userdata=0x81cb7e8) at seed-closure.c:290
#7 0x003aa316 in ?? () from /usr/lib/libffi.so.5
#8 0x003aa6fa in ?? () from /usr/lib/libffi.so.5
#9 0x00301151 in ?? () from /lib/libglib-2.0.so.0
#10 0x00303165 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#11 0x00306f88 in ?? () from /lib/libglib-2.0.so.0
#12 0x003074c7 in g_main_loop_run () from /lib/libglib-2.0.so.0
#13 0x0132c3c9 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#14 0x003aa63f in ffi_call_SYSV () from /usr/lib/libffi.so.5
#15 0x003aa46f in ffi_call () from /usr/lib/libffi.so.5
#16 0x0039c799 in g_function_info_invoke ()
from /usr/lib/libgirepository-1.0.so.0
#17 0x0013bb4a in seed_gobject_method_invoked (ctx=0xb636e098,
function=0xb5f3be80, this_object=0xb6338ac0, argumentCount=0,
arguments=0xbffff0d0, exception=0xbffff11c) at seed-engine.c:656
#18 0x00be20be in ?? () from /usr/lib/libwebkit-1.0.so.2
---Type <return> to continue, or q <return> to quit---
#19 0x00c28f1a in ?? () from /usr/lib/libwebkit-1.0.so.2
#20 0x02614236 in ?? ()
#21 0x00c3a7ce in ?? () from /usr/lib/libwebkit-1.0.so.2
#22 0x00cf5b66 in ?? () from /usr/lib/libwebkit-1.0.so.2
#23 0x00bdc4a9 in JSEvaluateScript () from /usr/lib/libwebkit-1.0.so.2
#24 0x0013860c in seed_evaluate (ctx=0xb67a2e24, s=0x80579c0, this=0x0)
at seed-api.c:279
#25 0x08048f01 in seed_exec (filename=0xbffff64c "thread_bugs.js") at
main.c:95
#26 0x08049134 in main (argc=2, argv=0xbffff4c4) at main.c:161

Running with --seed-debug=all says:
...
Clicked
** Message: [INVOCATION] seed-engine.c:532: Converting arg: func (0) of
function thread_create_full, exception is 0xbff862b4
** Message: [INVOCATION] seed-engine.c:532: Converting arg: data (1) of
function thread_create_full, exception is 0xbff862b4

** (seed:2209): WARNING **: ArgumentError - probably due to incorrect
gir file (which may be fixed upstream) argument 2 must not be null for
function: thread_create_full

** Message: [INVOCATION] seed-engine.c:532: Converting arg: stack_size
(2) of function thread_create_full, exception is 0xbff862b4
** Message: [INVOCATION] seed-engine.c:532: Converting arg: joinable (3)
of function thread_create_full, exception is 0xbff862b4
** Message: [INVOCATION] seed-engine.c:532: Converting arg: bound (4) of
function thread_create_full, exception is 0xbff862b4
** Message: [INVOCATION] seed-engine.c:532: Converting arg: priority (5)
of function thread_create_full, exception is 0xbff862b4
** Message: [INVOCATION] seed-engine.c:655: Invoking method:
thread_create_full with 6 'in' arguments and 0 'out' arguments
** Message: [IMPORTER] seed-importer.c:485:
seed_gi_importer_get_property with GLib
** Message: [IMPORTER] seed-importer.c:389: Using existing namespace ref
(0xb5bc3b40) for GLib
** Message: [IMPORTER] seed-importer.c:498: Result (0xb5bc3b40) from
attempting to import GLib: [object Object]
** Message: [INVOCATION] seed-closure.c:63: Invoking closure of type:
ThreadFunc

Thread start
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9ef4050. with priv->free_pointer = 0 with type: Thread, size:
2863311530
3.05975143636762e+17
Dispatch to mainloop
** Message: [INVOCATION] seed-engine.c:532: Converting arg: priority (0)
of function idle_add, exception is 0xb509be3c
** Message: [INVOCATION] seed-engine.c:532: Converting arg: function (1)
of function idle_add, exception is 0xb509be3c
** Message: [INVOCATION] seed-engine.c:532: Converting arg: data (2) of
function idle_add, exception is 0xb509be3c
** Message: [INVOCATION] seed-engine.c:532: Converting arg: notify (3)
of function idle_add, exception is 0xb509be3c
** Message: [INVOCATION] seed-engine.c:655: Invoking method: idle_add
with 4 'in' arguments and 0 'out' arguments
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd4520. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5180. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd51b0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5400. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5460. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd54c0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd54f0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5520. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5550. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5580. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd55b0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5600. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5630. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5660. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5690. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd56f0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5720. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5780. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd57b0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5800. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5830. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5950. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5980. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd59b0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5a00. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5a30. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5a60. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5a90. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5ac0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5ac0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5af0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5af0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5b20. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5b80. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd5b20. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6400. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6400. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6430. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6430. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6460. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6460. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6490. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6490. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd64c0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd64f0. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
** Message: [STRUCTS] seed-structs.c:50: Finalizing seed_pointer object
0x9dd6520. with priv->free_pointer = 0 with type: IBaseInfo, size: 0
Segmentation fault
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Follow-Ups:
- Re: libseed-list bug with threads and closures?
  - From: Jonatan Liljedahl

References:
- Re: libseed-list bug with threads and closures?
  - From: Jonatan Liljedahl

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