Re: [Qemu-devel] [PATCH 6/9] terminal3270: do not use backend timer sources

[Peter Xu <peterx@redhat.com>]

On Tue, Aug 28, 2018 at 12:23:19AM +0200, Marc-André Lureau wrote:
> terminal3270 is uses the front-end side of the chardev. It shouldn't
> create sources from backend side context. Fwiw, send_timing_mark_cb
> calls qemu_chr_fe_write_all() which should be thread safe.
> 
> This partially reverts changes from commit
> 2c716ba1506769c9be2caa02f0f6d6e7c00f4304.

I don't fully understand too on why "It shouldn't create sources from
backend side context".  Could you explain a bit?

If you don't want the backend gcontext to be exposed to the frontend,
IMHO the simplest thing is just to use the NULL gcontext in
qemu_chr_timeout_add_ms() which is a one-liner change. I don't see
much point on re-using the GSource tags since IMHO GSource pointer is
always superior to the old tag system.

> 
> CC: Peter Xu <peterx@redhat.com>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  hw/char/terminal3270.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/char/terminal3270.c b/hw/char/terminal3270.c
> index e9c45e55b1..35b079d5c4 100644
> --- a/hw/char/terminal3270.c
> +++ b/hw/char/terminal3270.c
> @@ -31,7 +31,7 @@ typedef struct Terminal3270 {
>      uint8_t outv[OUTPUT_BUFFER_SIZE];
>      int in_len;
>      bool handshake_done;
> -    GSource *timer_src;
> +    guint timer_tag;
>  } Terminal3270;
>  
>  #define TYPE_TERMINAL_3270 "x-terminal3270"
> @@ -47,10 +47,9 @@ static int terminal_can_read(void *opaque)
>  
>  static void terminal_timer_cancel(Terminal3270 *t)
>  {
> -    if (t->timer_src) {
> -        g_source_destroy(t->timer_src);
> -        g_source_unref(t->timer_src);
> -        t->timer_src = NULL;
> +    if (t->timer_tag) {
> +        g_source_remove(t->timer_tag);
> +        t->timer_tag = 0;
>      }
>  }
>  
> @@ -100,8 +99,7 @@ static void terminal_read(void *opaque, const uint8_t *buf, int size)
>      assert(size <= (INPUT_BUFFER_SIZE - t->in_len));
>  
>      terminal_timer_cancel(t);
> -    t->timer_src = qemu_chr_timeout_add_ms(t->chr.chr, 600 * 1000,
> -                                           send_timing_mark_cb, t);
> +    t->timer_tag = g_timeout_add_seconds(600, send_timing_mark_cb, t);
>      memcpy(&t->inv[t->in_len], buf, size);
>      t->in_len += size;
>      if (t->in_len < 2) {
> @@ -160,8 +158,7 @@ static void chr_event(void *opaque, int event)
>           * char-socket.c. Once qemu receives the terminal-type of the
>           * client, mark handshake done and trigger everything rolling again.
>           */
> -        t->timer_src = qemu_chr_timeout_add_ms(t->chr.chr, 600 * 1000,
> -                                               send_timing_mark_cb, t);
> +        t->timer_tag = g_timeout_add_seconds(600, send_timing_mark_cb, t);
>          break;
>      case CHR_EVENT_CLOSED:
>          sch->curr_status.scsw.dstat = SCSW_DSTAT_DEVICE_END;
> -- 
> 2.18.0.547.g1d89318c48
> 

Regards,

-- 
Peter Xu