[v8,2/5] coroutine: introduce coroutines API

diff --git a/Makefile.objs b/Makefile.objs
index 6991a9f..db907c4 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -11,6 +11,10 @@  oslib-obj-$(CONFIG_WIN32) += oslib-win32.o qemu-thread-win32.o
 oslib-obj-$(CONFIG_POSIX) += oslib-posix.o qemu-thread-posix.o
 
 #######################################################################
+# coroutines
+coroutine-obj-y = qemu-coroutine.o coroutine-gthread.o
+
+#######################################################################
 # block-obj-y is code used by both qemu system emulation and qemu-img
 
 block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o async.o
@@ -69,6 +73,7 @@  common-obj-y += readline.o console.o cursor.o qemu-error.o
 common-obj-y += $(oslib-obj-y)
 common-obj-$(CONFIG_WIN32) += os-win32.o
 common-obj-$(CONFIG_POSIX) += os-posix.o
+common-obj-y += $(coroutine-obj-y)
 
 common-obj-y += tcg-runtime.o host-utils.o
 common-obj-y += irq.o ioport.o input.o
diff --git a/coroutine-gthread.c b/coroutine-gthread.c
new file mode 100644
index 0000000..f09877e
--- /dev/null
+++ b/coroutine-gthread.c
@@ -0,0 +1,131 @@ 
+/*
+ * 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;
+    CoroutineAction action;
+} CoroutineGThread;
+
+static GCond *coroutine_cond;
+static GStaticMutex coroutine_lock = G_STATIC_MUTEX_INIT;
+static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT;
+
+static void __attribute__((constructor)) coroutine_init(void)
+{
+    if (!g_thread_supported()) {
+        g_thread_init(NULL);
+    }
+
+    coroutine_cond = g_cond_new();
+}
+
+static void coroutine_wait_runnable_locked(CoroutineGThread *co)
+{
+    while (!co->runnable) {
+        g_cond_wait(coroutine_cond, g_static_mutex_get_mutex(&coroutine_lock));
+    }
+}
+
+static void coroutine_wait_runnable(CoroutineGThread *co)
+{
+    g_static_mutex_lock(&coroutine_lock);
+    coroutine_wait_runnable_locked(co);
+    g_static_mutex_unlock(&coroutine_lock);
+}
+
+static gpointer coroutine_thread(gpointer opaque)
+{
+    CoroutineGThread *co = opaque;
+
+    g_static_private_set(&coroutine_key, co, NULL);
+    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 = qemu_mallocz(sizeof(*co));
+    co->thread = g_thread_create_full(coroutine_thread, co, 0, TRUE, TRUE,
+                                      G_THREAD_PRIORITY_NORMAL, NULL);
+    if (!co->thread) {
+        qemu_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);
+    qemu_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_static_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_static_mutex_unlock(&coroutine_lock);
+    return from->action;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    CoroutineGThread *co = g_static_private_get(&coroutine_key);
+
+    if (!co) {
+        co = qemu_mallocz(sizeof(*co));
+        co->runnable = true;
+        g_static_private_set(&coroutine_key, co, (GDestroyNotify)qemu_free);
+    }
+
+    return &co->base;
+}
+
+bool qemu_in_coroutine(void)
+{
+    CoroutineGThread *co = g_static_private_get(&coroutine_key);
+
+    return co && co->base.caller;
+}
diff --git a/qemu-coroutine-int.h b/qemu-coroutine-int.h
new file mode 100644
index 0000000..64915c2
--- /dev/null
+++ b/qemu-coroutine-int.h
@@ -0,0 +1,48 @@ 
+/*
+ * Coroutine internals
+ *
+ * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef QEMU_COROUTINE_INT_H
+#define QEMU_COROUTINE_INT_H
+
+#include "qemu-queue.h"
+#include "qemu-coroutine.h"
+
+typedef enum {
+    COROUTINE_YIELD = 1,
+    COROUTINE_TERMINATE = 2,
+} CoroutineAction;
+
+struct Coroutine {
+    CoroutineEntry *entry;
+    void *entry_arg;
+    Coroutine *caller;
+    QLIST_ENTRY(Coroutine) pool_next;
+};
+
+Coroutine *qemu_coroutine_new(void);
+void qemu_coroutine_delete(Coroutine *co);
+CoroutineAction qemu_coroutine_switch(Coroutine *from, Coroutine *to,
+                                      CoroutineAction action);
+
+#endif
diff --git a/qemu-coroutine.c b/qemu-coroutine.c
new file mode 100644
index 0000000..600be26
--- /dev/null
+++ b/qemu-coroutine.c
@@ -0,0 +1,75 @@ 
+/*
+ * QEMU coroutines
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>
+ *  Kevin Wolf         <kwolf@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "qemu-common.h"
+#include "qemu-coroutine.h"
+#include "qemu-coroutine-int.h"
+
+Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
+{
+    Coroutine *co = qemu_coroutine_new();
+    co->entry = entry;
+    return co;
+}
+
+static void coroutine_swap(Coroutine *from, Coroutine *to)
+{
+    CoroutineAction ret;
+
+    ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD);
+
+    switch (ret) {
+    case COROUTINE_YIELD:
+        return;
+    case COROUTINE_TERMINATE:
+        trace_qemu_coroutine_terminate(to);
+        qemu_coroutine_delete(to);
+        return;
+    default:
+        abort();
+    }
+}
+
+void qemu_coroutine_enter(Coroutine *co, void *opaque)
+{
+    Coroutine *self = qemu_coroutine_self();
+
+    trace_qemu_coroutine_enter(self, co, opaque);
+
+    if (co->caller) {
+        fprintf(stderr, "Co-routine re-entered recursively\n");
+        abort();
+    }
+
+    co->caller = self;
+    co->entry_arg = opaque;
+    coroutine_swap(self, co);
+}
+
+void coroutine_fn qemu_coroutine_yield(void)
+{
+    Coroutine *self = qemu_coroutine_self();
+    Coroutine *to = self->caller;
+
+    trace_qemu_coroutine_yield(self, to);
+
+    if (!to) {
+        fprintf(stderr, "Co-routine is yielding to no one\n");
+        abort();
+    }
+
+    self->caller = NULL;
+    coroutine_swap(self, to);
+}
diff --git a/qemu-coroutine.h b/qemu-coroutine.h
new file mode 100644
index 0000000..08255c7
--- /dev/null
+++ b/qemu-coroutine.h
@@ -0,0 +1,95 @@ 
+/*
+ * QEMU coroutine implementation
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_COROUTINE_H
+#define QEMU_COROUTINE_H
+
+#include <stdbool.h>
+
+/**
+ * Coroutines are a mechanism for stack switching and can be used for
+ * cooperative userspace threading.  These functions provide a simple but
+ * useful flavor of coroutines that is suitable for writing sequential code,
+ * rather than callbacks, for operations that need to give up control while
+ * waiting for events to complete.
+ *
+ * These functions are re-entrant and may be used outside the global mutex.
+ */
+
+/**
+ * Mark a function that executes in coroutine context
+ *
+ * Functions that execute in coroutine context cannot be called directly from
+ * normal functions.  In the future it would be nice to enable compiler or
+ * static checker support for catching such errors.  This annotation might make
+ * it possible and in the meantime it serves as documentation.
+ *
+ * For example:
+ *
+ *   static void coroutine_fn foo(void) {
+ *       ....
+ *   }
+ */
+#define coroutine_fn
+
+typedef struct Coroutine Coroutine;
+
+/**
+ * Coroutine entry point
+ *
+ * When the coroutine is entered for the first time, opaque is passed in as an
+ * argument.
+ *
+ * When this function returns, the coroutine is destroyed automatically and
+ * execution continues in the caller who last entered the coroutine.
+ */
+typedef void coroutine_fn CoroutineEntry(void *opaque);
+
+/**
+ * Create a new coroutine
+ *
+ * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
+ */
+Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
+
+/**
+ * Transfer control to a coroutine
+ *
+ * The opaque argument is passed as the argument to the entry point when
+ * entering the coroutine for the first time.  It is subsequently ignored.
+ */
+void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
+
+/**
+ * Transfer control back to a coroutine's caller
+ *
+ * This function does not return until the coroutine is re-entered using
+ * qemu_coroutine_enter().
+ */
+void coroutine_fn qemu_coroutine_yield(void);
+
+/**
+ * Get the currently executing coroutine
+ */
+Coroutine *coroutine_fn qemu_coroutine_self(void);
+
+/**
+ * Return whether or not currently inside a coroutine
+ *
+ * This can be used to write functions that work both when in coroutine context
+ * and when not in coroutine context.  Note that such functions cannot use the
+ * coroutine_fn annotation since they work outside coroutine context.
+ */
+bool qemu_in_coroutine(void);
+
+#endif /* QEMU_COROUTINE_H */
diff --git a/trace-events b/trace-events
index 713f042..136f775 100644
--- a/trace-events
+++ b/trace-events
@@ -425,3 +425,8 @@  disable qemu_put_ram_ptr(void* addr) "%p"
 
 # hw/xen_platform.c
 disable xen_platform_log(char *s) "xen platform: %s"
+
+# qemu-coroutine.c
+disable qemu_coroutine_enter(void *from, void *to, void *opaque) "from %p to %p opaque %p"
+disable qemu_coroutine_yield(void *from, void *to) "from %p to %p"
+disable qemu_coroutine_terminate(void *co) "self %p"