Re: [Qemu-devel] [PATCH 1/3] colo-compare: serialize compare thread's initialization with main thread

[Jason Wang <jasowang@redhat.com>]

On 2017年04月20日 15:46, zhanghailiang wrote:
> We call qemu_chr_fe_set_handlers() in colo-compare thread, it is used
> to detach watched fd from default main context, so it has chance to
> handle the same watched fd with main thread concurrently, which will
> trigger an error report:
> "qemu-char.c:918: io_watch_poll_finalize: Assertion `iwp->src == ((void *)0)' failed."

Anyway to prevent fd from being handled by main thread before creating 
colo thread? Using semaphore seems not elegant.

Thanks

>
> Fix it by serializing compare thread's initialization with main thread.
>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>   net/colo-compare.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index 54e6d40..a6bf419 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -83,6 +83,7 @@ typedef struct CompareState {
>       GHashTable *connection_track_table;
>       /* compare thread, a thread for each NIC */
>       QemuThread thread;
> +    QemuSemaphore thread_ready;
>   
>       GMainContext *worker_context;
>       GMainLoop *compare_loop;
> @@ -557,6 +558,8 @@ static void *colo_compare_thread(void *opaque)
>                             (GSourceFunc)check_old_packet_regular, s, NULL);
>       g_source_attach(timeout_source, s->worker_context);
>   
> +    qemu_sem_post(&s->thread_ready);
> +
>       g_main_loop_run(s->compare_loop);
>   
>       g_source_unref(timeout_source);
> @@ -707,12 +710,15 @@ static void colo_compare_complete(UserCreatable *uc, Error **errp)
>                                                         connection_key_equal,
>                                                         g_free,
>                                                         connection_destroy);
> +    qemu_sem_init(&s->thread_ready, 0);
>   
>       sprintf(thread_name, "colo-compare %d", compare_id);
>       qemu_thread_create(&s->thread, thread_name,
>                          colo_compare_thread, s,
>                          QEMU_THREAD_JOINABLE);
>       compare_id++;
> +    qemu_sem_wait(&s->thread_ready);
> +    qemu_sem_destroy(&s->thread_ready);
>   
>       return;
>   }