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Re: Emitting signals from threads




On Tue, 8 Jan 2019 10:02:58 -0800
Mitko Haralanov via gtk-list <gtk-list@xxxxxxxxx> wrote:
> Thanks for the reply.
> 
> When calling g_main_context_invoke_full(), I am using NULL as the
> context pointer. According to the documentation of
> g_main_context_invoke():
> 
>         "If context is NULL then the global default main context — as
> returned by g_main_context_default() — is used."
> 
> So, the code should be using the correct context.
> 
> One of the main reasons why I am not using g_idle_add() is the timing
> of the callback. I don't want to defer the processing of the callback
> to the "idle" time since this is signal handling related. Another
> advantage of g_main_context_invoke[_full]() is that it will check the
> "context" of the caller and, if possible, will call the callback
> directly:
> 
>        "If context is owned by the current thread, function is called
> directly. Otherwise, if context is the thread-default main context of
> the current thread and g_main_context_acquire()
>        succeeds, then function is called and g_main_context_release()
> is called afterwards.
>        In any other case, an idle source is created to call function
> and that source is attached to context (presumably to be run in
> another thread). The idle source is attached with
>        G_PRIORITY_DEFAULT priority. If you want a different priority,
> use g_main_context_invoke_full()."
> 
> Your suggested implementation is basically the GLib's async queues.
> Or, may be, a custom event source. However, it seems that
> g_main_context_invoke_full() should be doing exactly that. With all
> due respect, I also don't see how it would solve the issue. If the
> current implementation has an problem with locking/race conditions,
> would your suggested implementation suffer from the same issue since
> it's using the same or similar mechanism for calling the callback?

"With all due respect" this is fine, but I am not sure what more your
interlocutor can say.  If your code works with g_idle_add() but not
with g_main_context_invoke_full() then you have a timing issue in your
code caused by the fact that the callbacks for the default main loop via
g_main_context_invoke_full() may be executed before the callbacks for
earlier invocations of g_idle_add().

If it doesn't work with either of them then you have some other issue.
It is possible you have found a bug in glib but more likely you have
found a bug in your code.
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