coroutine: move into libqemuutil.a library

The coroutine files are currently referenced by the block-obj-y
variable. The coroutine functionality though is already used by
more than just the block code. eg migration code uses coroutine
yield. In the future the I/O channel code will also use the
coroutine yield functionality. Since the coroutine code is nicely
self-contained it can be easily built as part of the libqemuutil.a
library, making it widely available.

The headers are also moved into include/qemu, instead of the
include/block directory, since they are now part of the util
codebase, and the impl was never in the block/ directory
either.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

util/coroutine-gthread.c

@@ -0,0 +1,198 @@
+/*
+ * GThread coroutine initialization code
+ *
+ * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2011  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.0 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <glib.h>
+#include "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+typedef struct {
+    Coroutine base;
+    GThread *thread;
+    bool runnable;
+    bool free_on_thread_exit;
+    CoroutineAction action;
+} CoroutineGThread;
+
+static CompatGMutex coroutine_lock;
+static CompatGCond coroutine_cond;
+
+/* GLib 2.31 and beyond deprecated various parts of the thread API,
+ * but the new interfaces are not available in older GLib versions
+ * so we have to cope with both.
+ */
+#if GLIB_CHECK_VERSION(2, 31, 0)
+/* Awkwardly, the GPrivate API doesn't provide a way to update the
+ * GDestroyNotify handler for the coroutine key dynamically. So instead
+ * we track whether or not the CoroutineGThread should be freed on
+ * thread exit / coroutine key update using the free_on_thread_exit
+ * field.
+ */
+static void coroutine_destroy_notify(gpointer data)
+{
+    CoroutineGThread *co = data;
+    if (co && co->free_on_thread_exit) {
+        g_free(co);
+    }
+}
+
+static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify);
+
+static inline CoroutineGThread *get_coroutine_key(void)
+{
+    return g_private_get(&coroutine_key);
+}
+
+static inline void set_coroutine_key(CoroutineGThread *co,
+                                     bool free_on_thread_exit)
+{
+    /* Unlike g_static_private_set() this does not call the GDestroyNotify
+     * if the previous value of the key was NULL. Fortunately we only need
+     * the GDestroyNotify in the non-NULL key case.
+     */
+    co->free_on_thread_exit = free_on_thread_exit;
+    g_private_replace(&coroutine_key, co);
+}
+
+static inline GThread *create_thread(GThreadFunc func, gpointer data)
+{
+    return g_thread_new("coroutine", func, data);
+}
+
+#else
+
+/* Handle older GLib versions */
+
+static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT;
+
+static inline CoroutineGThread *get_coroutine_key(void)
+{
+    return g_static_private_get(&coroutine_key);
+}
+
+static inline void set_coroutine_key(CoroutineGThread *co,
+                                     bool free_on_thread_exit)
+{
+    g_static_private_set(&coroutine_key, co,
+                         free_on_thread_exit ? (GDestroyNotify)g_free : NULL);
+}
+
+static inline GThread *create_thread(GThreadFunc func, gpointer data)
+{
+    return g_thread_create_full(func, data, 0, TRUE, TRUE,
+                                G_THREAD_PRIORITY_NORMAL, NULL);
+}
+
+#endif
+
+
+static void __attribute__((constructor)) coroutine_init(void)
+{
+#if !GLIB_CHECK_VERSION(2, 31, 0)
+    if (!g_thread_supported()) {
+        g_thread_init(NULL);
+    }
+#endif
+}
+
+static void coroutine_wait_runnable_locked(CoroutineGThread *co)
+{
+    while (!co->runnable) {
+        g_cond_wait(&coroutine_cond, &coroutine_lock);
+    }
+}
+
+static void coroutine_wait_runnable(CoroutineGThread *co)
+{
+    g_mutex_lock(&coroutine_lock);
+    coroutine_wait_runnable_locked(co);
+    g_mutex_unlock(&coroutine_lock);
+}
+
+static gpointer coroutine_thread(gpointer opaque)
+{
+    CoroutineGThread *co = opaque;
+
+    set_coroutine_key(co, false);
+    coroutine_wait_runnable(co);
+    co->base.entry(co->base.entry_arg);
+    qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE);
+    return NULL;
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+    CoroutineGThread *co;
+
+    co = g_malloc0(sizeof(*co));
+    co->thread = create_thread(coroutine_thread, co);
+    if (!co->thread) {
+        g_free(co);
+        return NULL;
+    }
+    return &co->base;
+}
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+    CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_);
+
+    g_thread_join(co->thread);
+    g_free(co);
+}
+
+CoroutineAction qemu_coroutine_switch(Coroutine *from_,
+                                      Coroutine *to_,
+                                      CoroutineAction action)
+{
+    CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_);
+    CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_);
+
+    g_mutex_lock(&coroutine_lock);
+    from->runnable = false;
+    from->action = action;
+    to->runnable = true;
+    to->action = action;
+    g_cond_broadcast(&coroutine_cond);
+
+    if (action != COROUTINE_TERMINATE) {
+        coroutine_wait_runnable_locked(from);
+    }
+    g_mutex_unlock(&coroutine_lock);
+    return from->action;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    CoroutineGThread *co = get_coroutine_key();
+    if (!co) {
+        co = g_malloc0(sizeof(*co));
+        co->runnable = true;
+        set_coroutine_key(co, true);
+    }
+
+    return &co->base;
+}
+
+bool qemu_in_coroutine(void)
+{
+    CoroutineGThread *co = get_coroutine_key();
+
+    return co && co->base.caller;
+}