Archipelago » qemu

/*

 * 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 "block/coroutine_int.h"

typedef struct {

    Coroutine base;

    GThread *thread;

    bool runnable;

    bool free_on_thread_exit;

    CoroutineAction action;

} CoroutineGThread;

static GStaticMutex coroutine_lock = G_STATIC_MUTEX_INIT;

/* 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)

/* Default zero-initialisation is sufficient for 2.31+ GCond */

static GCond the_coroutine_cond;

static GCond *coroutine_cond = &the_coroutine_cond;

static inline void init_coroutine_cond(void)

{

}

/* 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 GCond *coroutine_cond;

static inline void init_coroutine_cond(void)

{

    coroutine_cond = g_cond_new();

}

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 (!g_thread_supported()) {

#if !GLIB_CHECK_VERSION(2, 31, 0)

        g_thread_init(NULL);

#else

        fprintf(stderr, "glib threading failed to initialize.\n");

        exit(1);

#endif

    }

    init_coroutine_cond();

}

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;

    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_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 = 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;

}