Re: [Qemu-devel] [PATCH] coroutine-gthread.c: Avoid threading APIs deprecated in GLib 2.31

[Peter Maydell]

Ping?

On 3 March 2012 14:52, Peter Maydell <address@hidden> wrote:
> The GLib threading APIs were revamped in GLib 2.31 and a number
> of the old interfaces were deprecated, which means they provoke
> compilation warnings (errors if -Werror) now. Add support for the
> new interfaces while retaining the old ones so we can still compile
> on older versions of GLib too.
>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> In particular, this fixes compilation failure on ARM hosts running
> Ubuntu Precise. Seems kinda ugly to me, suggestions for improvement
> welcomed.
>
>  coroutine-gthread.c |   96 
> ++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 files changed, 87 insertions(+), 9 deletions(-)
>
> diff --git a/coroutine-gthread.c b/coroutine-gthread.c
> index 662801b..30c24c9 100644
> --- a/coroutine-gthread.c
> +++ b/coroutine-gthread.c
> @@ -26,13 +26,93 @@ typedef struct {
>     Coroutine base;
>     GThread *thread;
>     bool runnable;
> +    bool free_on_thread_exit;
>     CoroutineAction action;
>  } CoroutineGThread;
>
> -static GCond *coroutine_cond;
>  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()) {
> @@ -44,7 +124,7 @@ static void __attribute__((constructor)) 
> coroutine_init(void)
>  #endif
>     }
>
> -    coroutine_cond = g_cond_new();
> +    init_coroutine_cond();
>  }
>
>  static void coroutine_wait_runnable_locked(CoroutineGThread *co)
> @@ -65,7 +145,7 @@ static gpointer coroutine_thread(gpointer opaque)
>  {
>     CoroutineGThread *co = opaque;
>
> -    g_static_private_set(&coroutine_key, co, NULL);
> +    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);
> @@ -77,8 +157,7 @@ Coroutine *qemu_coroutine_new(void)
>     CoroutineGThread *co;
>
>     co = g_malloc0(sizeof(*co));
> -    co->thread = g_thread_create_full(coroutine_thread, co, 0, TRUE, TRUE,
> -                                      G_THREAD_PRIORITY_NORMAL, NULL);
> +    co->thread = create_thread(coroutine_thread, co);
>     if (!co->thread) {
>         g_free(co);
>         return NULL;
> @@ -117,12 +196,11 @@ CoroutineAction qemu_coroutine_switch(Coroutine *from_,
>
>  Coroutine *qemu_coroutine_self(void)
>  {
> -    CoroutineGThread *co = g_static_private_get(&coroutine_key);
> -
> +    CoroutineGThread *co = get_coroutine_key();
>     if (!co) {
>         co = g_malloc0(sizeof(*co));
>         co->runnable = true;
> -        g_static_private_set(&coroutine_key, co, (GDestroyNotify)g_free);
> +        set_coroutine_key(co, true);
>     }
>
>     return &co->base;
> @@ -130,7 +208,7 @@ Coroutine *qemu_coroutine_self(void)
>
>  bool qemu_in_coroutine(void)
>  {
> -    CoroutineGThread *co = g_static_private_get(&coroutine_key);
> +    CoroutineGThread *co = get_coroutine_key();
>
>     return co && co->base.caller;
>  }
> --
> 1.7.5.4