[Spice-devel] [PATCH 1/3] spicevmc: store channel in char device

[Frediano Ziglio]

> Store the channel in the char device object, and unref it in dispose.
> Previously, we were just creating a channel and potentially allowing it
> to leak.  There may be better long-term solutions, but this works for
> now.
> ---
> Changes from last version:
>  - set channel to NULL in spicevmc_device_disconnect() to avoid the
>  double-free
>    mentioned by Frediano
> 

I was considering 1/3 and 3/3 patches. Would make sense to
have just the spicevmc_device_disconnect (and similar smartcard) to just
unref the device however g_clear_object on chardev is not enough:
- device destruction should call reds_unregister_channel to prevent
  possible future RedChannelClient to connect to the channel;
- destruction should call red_channel_destroy and not just g_object_unref
  (called by g_clear_object) to close current clients (no reasons to have
  client to handle closed devices).
Note that the above cannot/shouldn't be moved to the channel destructor
as there will be external (like from RedChannelClient) reference to
the channel that will prevent these stuff to be executed.

Possibly there could be a red_char_device_clear_channel(RedChannel **p_channel)
utility that check NULL pointer and do all these stuff to be called
by Smartcard/SpiceVmc instead of g_clear_pointer.

>  server/spicevmc.c | 46 ++++++++++++++++++++++++++++++----------------
>  1 file changed, 30 insertions(+), 16 deletions(-)
> 
> diff --git a/server/spicevmc.c b/server/spicevmc.c
> index 7067bc7..8e23248 100644
> --- a/server/spicevmc.c
> +++ b/server/spicevmc.c
> @@ -47,6 +47,9 @@
>  #define BUF_SIZE (64 * 1024 + 32)
>  #define COMPRESS_THRESHOLD 1000
>  
> +typedef struct RedVmcChannel RedVmcChannel;
> +typedef struct RedVmcChannelClass RedVmcChannelClass;
> +
>  typedef struct RedVmcPipeItem {
>      RedPipeItem base;
>  
> @@ -75,6 +78,7 @@ typedef struct RedCharDeviceSpiceVmcClass
> RedCharDeviceSpiceVmcClass;
>  
>  struct RedCharDeviceSpiceVmc {
>      RedCharDevice parent;
> +    RedVmcChannel *channel;
>  };
>  
>  struct RedCharDeviceSpiceVmcClass
> @@ -89,9 +93,6 @@ static RedCharDevice
> *red_char_device_spicevmc_new(SpiceCharDeviceInstance *sin,
>  
>  G_DEFINE_TYPE(RedCharDeviceSpiceVmc, red_char_device_spicevmc,
>  RED_TYPE_CHAR_DEVICE)
>  
> -#define RED_CHAR_DEVICE_SPICEVMC_PRIVATE(o) \
> -    (G_TYPE_INSTANCE_GET_PRIVATE ((o), RED_TYPE_CHAR_DEVICE_SPICEVMC,
> RedCharDeviceSpiceVmcPrivate))
> -
>  #define RED_TYPE_VMC_CHANNEL red_vmc_channel_get_type()
>  
>  #define RED_VMC_CHANNEL(obj) \
> @@ -103,9 +104,6 @@ G_DEFINE_TYPE(RedCharDeviceSpiceVmc,
> red_char_device_spicevmc, RED_TYPE_CHAR_DEV
>  #define RED_VMC_CHANNEL_GET_CLASS(obj) \
>      (G_TYPE_INSTANCE_GET_CLASS((obj), RED_TYPE_VMC_CHANNEL,
>      RedVmcChannelClass))
>  
> -typedef struct RedVmcChannel RedVmcChannel;
> -typedef struct RedVmcChannelClass RedVmcChannelClass;
> -
>  struct RedVmcChannel
>  {
>      RedChannel parent;
> @@ -855,28 +853,33 @@ RedCharDevice *spicevmc_device_connect(RedsState *reds,
>                                         SpiceCharDeviceInstance *sin,
>                                         uint8_t channel_type)
>  {
> +    RedCharDeviceSpiceVmc *dev_state;
>      RedVmcChannel *state = red_vmc_channel_new(reds, channel_type, sin);
>  
> -    return state->chardev;
> +    dev_state = RED_CHAR_DEVICE_SPICEVMC(state->chardev);
> +    dev_state->channel = state;
> +
> +    return RED_CHAR_DEVICE(dev_state);
>  }
>  
>  /* Must be called from RedClient handling thread. */
>  void spicevmc_device_disconnect(RedsState *reds, SpiceCharDeviceInstance
>  *sin)
>  {
> -    RedVmcChannel *state;
> +    RedVmcChannel *channel;
> +    RedCharDeviceSpiceVmc *vmc = RED_CHAR_DEVICE_SPICEVMC(sin->st);
>  
> -    /* FIXME */
> -    state = (RedVmcChannel
> *)red_char_device_opaque_get((RedCharDevice*)sin->st);
> +    channel = vmc->channel;
> +    vmc->channel = NULL;
>  
> -    red_char_device_write_buffer_release(state->chardev,
> &state->recv_from_client_buf);
> +    red_char_device_write_buffer_release(channel->chardev,
> &channel->recv_from_client_buf);
>      /* FIXME */
> -    red_char_device_destroy((RedCharDevice*)sin->st);
> -    state->chardev = NULL;
> +    red_char_device_destroy(RED_CHAR_DEVICE(vmc));
> +    channel->chardev = NULL;
>      sin->st = NULL;
>  
> -    reds_unregister_channel(reds, RED_CHANNEL(state));
> -    free(state->pipe_item);
> -    red_channel_destroy(RED_CHANNEL(state));
> +    reds_unregister_channel(reds, RED_CHANNEL(channel));
> +    free(channel->pipe_item);
> +    red_channel_destroy(RED_CHANNEL(channel));
>  }
>  
>  SPICE_GNUC_VISIBLE void spice_server_port_event(SpiceCharDeviceInstance
>  *sin, uint8_t event)
> @@ -904,10 +907,21 @@ SPICE_GNUC_VISIBLE void
> spice_server_port_event(SpiceCharDeviceInstance *sin, ui
>  }
>  
>  static void
> +red_char_device_spicevmc_dispose(GObject *object)
> +{
> +    RedCharDeviceSpiceVmc *self = RED_CHAR_DEVICE_SPICEVMC(object);
> +
> +    g_clear_object(&self->channel);
> +}
> +
> +static void
>  red_char_device_spicevmc_class_init(RedCharDeviceSpiceVmcClass *klass)
>  {
> +    GObjectClass *object_class = G_OBJECT_CLASS(klass);
>      RedCharDeviceClass *char_dev_class = RED_CHAR_DEVICE_CLASS(klass);
>  
> +    object_class->dispose = red_char_device_spicevmc_dispose;
> +
>      char_dev_class->read_one_msg_from_device =
>      spicevmc_chardev_read_msg_from_dev;
>      char_dev_class->send_msg_to_client =
>      spicevmc_chardev_send_msg_to_client;
>      char_dev_class->send_tokens_to_client =
>      spicevmc_char_dev_send_tokens_to_client;

Otherwise the patch is good. My proposal can apply to this patch as
a change or future change either.

Frediano