On Thu, 22 Dec 2005, michael meeks wrote:
---------- Forwarded message ----------
Date: Tue, 20 Dec 2005 17:21:07 +0000
From: michael meeks <[EMAIL PROTECTED]>
To: Federico Mena Quintero <[EMAIL PROTECTED]>, Tim Janik
<[EMAIL PROTECTED]>
Cc: Gtk Hackers <gtk-devel-list@gnome.org>
Subject: missing GMainContext methods ...
So,
I sent this a while back - but didn't see it on the list - perhaps
broken subscription information (?).
I append a patch implementing these two to some level.
On Thu, 2005-11-17 at 16:57 +0000, michael meeks wrote:
So - I've been trying to use the GMainContext to fix a rather tricky
issue in using unsafe single-threaded code accessed via ORBit2 from
multiple OO.o threads in a safe & reliable way. This is somewhat
involved, for various reasons, but made particularly unpleasant due to 2
missing methods:
a) gboolean g_main_context_is_owner (GMainContext *context);
+ this would tell you if the current thread owns the
g_main_context. NB. this is subtly different from
something like:
if (g_main_context_acquire ()) {
g_main_context_release();
... I own it - horay ...
}
+ since that actually transiently takes ownership of
the thread but doesn't tell you if you (now) contine
to own it [ due to some (much) higher stack frame
having taken that lock ].
i think this should go in, with one modification:
+gboolean
+g_main_context_is_owner (GMainContext *context)
+{
+ gboolean is_owner;
+
+ if (!context)
+ context = g_main_context_default ();
+
+#ifdef G_THREADS_ENABLED
+ LOCK_CONTEXT (context);
+ is_owner = context->owner == G_THREAD_SELF;
+ UNLOCK_CONTEXT (context);
+#else
+ is_owner = TRUE;
+#endif
+
+ return is_owner;
+}
if (!context), the function should simply return FALSE, instead of
forcefully create a context. following the basic principle of eliminating
side-effects on getters/queries.
b) void g_main_context_acquire_with_wakeup (GMainContext *context);
+ this cunning method - would be the analogue of
g_main_context_wait () - except instead of sitting
around hoping that the other thread doing the poll
will wake-up, it does a (safe) g_main_context_wakeup
with the relevant locks held;
+ currently it appears impossible/acutely-ugly to
get ownership of the GMainContext from another thread
if the main thread is in it's poll.
this looks good to me as is:
+void
+g_main_context_acquire_with_wakeup (GMainContext *context)
+{
+ gboolean got_ownership;
+
+ if (!context)
+ context = g_main_context_default ();
+
+ got_ownership = g_main_context_acquire (context);
+ while (!got_ownership)
+ {
+ LOCK_CONTEXT (context);
+ g_main_context_wakeup_unlocked (context);
+ got_ownership = g_main_context_wait (context,
+ context->cond,
+ g_static_mutex_get_mutex
(&context->mutex));
+ UNLOCK_CONTEXT (context);
+ }
+}
The basic reasoning here is that - ~all existing event-driven gtk+
code, typically happens from the default GMainContext, and/or at least
that provides a reasonable back-compatible way to create a backwards
compatible 'apartment' (by holding the GMainContext lock) to execute old
code in in-line.
I attach a simple patch; the g_main_context_is_owner impl. is of
course
trivial - it'd be great to be able to commit that by itself. The
'acquire_with_wakeup' is also relatively trivial, cf. above.
There is no bugzilla number, is that a problem ?
i don't think so. unless owen vetos in, i'll apply them tomorrow with
the change outlined above.
Thanks,
Michael.
--
[EMAIL PROTECTED] <><, Pseudo Engineer, itinerant idiot
---
ciaoTJ
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