glib-compat.h: add new thread API emulation on top of pre-2.31 API

Thread API changed in glib-2.31 significantly.  Before that version,
conditionals and mutexes were only allocated dynamically, using
_new()/_free() interface.  in 2.31 and up, they're allocated statically
as regular variables, and old interface is deprecated.

(Note: glib docs says the new interface is available since version
2.32, but it was actually introduced in version 2.31).

Create the new interface using old primitives, by providing non-opaque
definitions of the base types (GCond and GMutex) using GOnces.

Replace #ifdeffery around GCond and GMutex in trace/simple.c and
coroutine-gthread.c too because it does not work anymore with the new
glib-compat.h.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[Use GOnce to support lazy initialization; introduce CompatGMutex
 and CompatGCond.  - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/glib-compat.h

@@ -5,6 +5,8 @@
  *
  * Authors:
  *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Michael Tokarev   <mjt@tls.msk.ru>
+ *  Paolo Bonzini     <pbonzini@redhat.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
@@ -43,4 +45,121 @@ static inline gint g_poll(GPollFD *fds, guint nfds, gint timeout)
 }
 #endif
 
+#if !GLIB_CHECK_VERSION(2, 31, 0)
+/* before glib-2.31, GMutex and GCond was dynamic-only (there was a separate
+ * GStaticMutex, but it didn't work with condition variables).
+ *
+ * Our implementation uses GOnce to fake a static implementation that does
+ * not require separate initialization.
+ * We need to rename the types to avoid passing our CompatGMutex/CompatGCond
+ * by mistake to a function that expects GMutex/GCond.  However, for ease
+ * of use we keep the GLib function names.  GLib uses macros for the
+ * implementation, we use inline functions instead and undefine the macros.
+ */
+
+typedef struct CompatGMutex {
+    GOnce once;
+} CompatGMutex;
+
+typedef struct CompatGCond {
+    GOnce once;
+} CompatGCond;
+
+static inline gpointer do_g_mutex_new(gpointer unused)
+{
+    return (gpointer) g_mutex_new();
+}
+
+static inline void g_mutex_init(CompatGMutex *mutex)
+{
+    mutex->once = (GOnce) G_ONCE_INIT;
+}
+
+static inline void g_mutex_clear(CompatGMutex *mutex)
+{
+    assert(mutex->once.status != G_ONCE_STATUS_PROGRESS);
+    if (mutex->once.retval) {
+        g_mutex_free((GMutex *) mutex->once.retval);
+    }
+    mutex->once = (GOnce) G_ONCE_INIT;
+}
+
+static inline void (g_mutex_lock)(CompatGMutex *mutex)
+{
+    g_once(&mutex->once, do_g_mutex_new, NULL);
+    g_mutex_lock((GMutex *) mutex->once.retval);
+}
+#undef g_mutex_lock
+
+static inline gboolean (g_mutex_trylock)(CompatGMutex *mutex)
+{
+    g_once(&mutex->once, do_g_mutex_new, NULL);
+    return g_mutex_trylock((GMutex *) mutex->once.retval);
+}
+#undef g_mutex_trylock
+
+
+static inline void (g_mutex_unlock)(CompatGMutex *mutex)
+{
+    g_mutex_unlock((GMutex *) mutex->once.retval);
+}
+#undef g_mutex_unlock
+
+static inline gpointer do_g_cond_new(gpointer unused)
+{
+    return (gpointer) g_cond_new();
+}
+
+static inline void g_cond_init(CompatGCond *cond)
+{
+    cond->once = (GOnce) G_ONCE_INIT;
+}
+
+static inline void g_cond_clear(CompatGCond *cond)
+{
+    assert(cond->once.status != G_ONCE_STATUS_PROGRESS);
+    if (cond->once.retval) {
+        g_cond_free((GCond *) cond->once.retval);
+    }
+    cond->once = (GOnce) G_ONCE_INIT;
+}
+
+static inline void (g_cond_wait)(CompatGCond *cond, CompatGMutex *mutex)
+{
+    assert(mutex->once.status != G_ONCE_STATUS_PROGRESS);
+    g_once(&cond->once, do_g_cond_new, NULL);
+    g_cond_wait((GCond *) cond->once.retval, (GMutex *) mutex->once.retval);
+}
+#undef g_cond_wait
+
+static inline void (g_cond_broadcast)(CompatGCond *cond)
+{
+    g_once(&cond->once, do_g_cond_new, NULL);
+    g_cond_broadcast((GCond *) cond->once.retval);
+}
+#undef g_cond_broadcast
+
+static inline void (g_cond_signal)(CompatGCond *cond)
+{
+    g_once(&cond->once, do_g_cond_new, NULL);
+    g_cond_signal((GCond *) cond->once.retval);
+}
+#undef g_cond_signal
+
+
+/* before 2.31 there was no g_thread_new() */
+static inline GThread *g_thread_new(const char *name,
+                                    GThreadFunc func, gpointer data)
+{
+    GThread *thread = g_thread_create(func, data, TRUE, NULL);
+    if (!thread) {
+        g_error("creating thread");
+    }
+    return thread;
+}
+#else
+#define CompatGMutex GMutex
+#define CompatGCond GCond
+#endif /* glib 2.31 */
+
 #endif