[Spice-devel] [PATCH v7 06/14] usbredir: Spawn a different thread for device redirection flow

[Jonathon Jongsma]

On Wed, 2016-03-16 at 10:41 -0500, Jonathon Jongsma wrote:
> So, after adding the g_task_return_boolean back to _open_device_async_cb(), I
> noticed that since g_task_return_error() can potentially complete the task
> immediately (rather than in an idle handler done previously), we may be
> executing the GAsyncReadyCallback while the channel is locked. Currently, I
> don't think this causes any problems, but if the callback did anything that
> required locking the channel's mutex, that could result in a deadlock. So
> here's
> an additional proposed patch to unlock before completing the task. If this
> change is ACKed, I'd probably squash it into this patch.
> 
> ------------
> diff --git a/src/channel-usbredir.c b/src/channel-usbredir.c
> index cd2ff4f..aa8e943 100644
> --- a/src/channel-usbredir.c
> +++ b/src/channel-usbredir.c
> @@ -367,17 +367,19 @@ _open_device_async_cb(GTask *task,
>  
>      spice_usbredir_channel_lock(channel);
>  
> -    if (!spice_usbredir_channel_open_device(channel, &err)) {
> +    spice_usbredir_channel_open_device(channel, &err);
> +    libusb_unref_device(priv->device);
> +    priv->device = NULL;
> +    g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
> +    priv->spice_device = NULL;
> +
> +    spice_usbredir_channel_unlock(channel);
> +
> +    if (err) {
>          g_task_return_error(task, err);
> -        libusb_unref_device(priv->device);
> -        priv->device = NULL;
> -        g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
> -        priv->spice_device = NULL;
>      } else {
>          g_task_return_boolean(task, TRUE);
>      }
> -
> -    spice_usbredir_channel_unlock(channel);
>  }
>  #endif
>  

... And Fabiano pointed out that this patch is incorrect since it frees the
device even if it was successfully redirected. That's clearly wrong. New patch
coming.


> 
> 
> On Wed, 2016-03-16 at 10:16 -0500, Jonathon Jongsma wrote:
> > On Wed, 2016-03-16 at 11:27 +0100, Christophe Fergeau wrote:
> > > Hey,
> > > 
> > > On Tue, Mar 15, 2016 at 02:31:03PM -0500, Jonathon Jongsma wrote:
> > > > +#ifndef USE_POLKIT
> > > > +static void
> > > > +_open_device_async_cb(GTask *task,
> > > > +                      gpointer object,
> > > > +                      gpointer task_data,
> > > > +                      GCancellable *cancellable)
> > > > +{
> > > > +    GError *err = NULL;
> > > > +    SpiceUsbredirChannel *channel = SPICE_USBREDIR_CHANNEL(object);
> > > > +    SpiceUsbredirChannelPrivate *priv = channel->priv;
> > > > +
> > > > +    spice_usbredir_channel_lock(channel);
> > > > +
> > > > +    if (!spice_usbredir_channel_open_device(channel, &err)) {
> > > > +        g_task_return_error(task, err);
> > > > +        libusb_unref_device(priv->device);
> > > > +        priv->device = NULL;
> > > > +        g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
> > > > +        priv->spice_device = NULL;
> > > > +    }
> > > > +
> > > > +    spice_usbredir_channel_unlock(channel);
> > > > +}
> > > > +#endif
> > > > +
> > > >  G_GNUC_INTERNAL
> > > >  void spice_usbredir_channel_connect_device_async(
> > > >                                            SpiceUsbredirChannel
> > > > *channel,
> > > > @@ -331,9 +356,6 @@ void spice_usbredir_channel_connect_device_async(
> > > >  {
> > > >      SpiceUsbredirChannelPrivate *priv = channel->priv;
> > > >      GTask *task;
> > > > -#ifndef USE_POLKIT
> > > > -    GError *err = NULL;
> > > > -#endif
> > > >  
> > > >      g_return_if_fail(SPICE_IS_USBREDIR_CHANNEL(channel));
> > > >      g_return_if_fail(device != NULL);
> > > > @@ -376,15 +398,7 @@ void spice_usbredir_channel_connect_device_async(
> > > >                                          channel);
> > > >      return;
> > > >  #else
> > > > -    if (!spice_usbredir_channel_open_device(channel, &err)) {
> > > > -        g_task_return_error(task, err);
> > > > -        libusb_unref_device(priv->device);
> > > > -        priv->device = NULL;
> > > > -        g_boxed_free(spice_usb_device_get_type(), priv->spice_device);
> > > > -        priv->spice_device = NULL;
> > > > -    } else {
> > > > -        g_task_return_boolean(task, TRUE);
> > > 
> > > Only looked at the diff, not at the full code, but this
> > > g_task_return_boolean(task, TRUE); is gone from the threaded version, is
> > > this intentional?
> > > 
> > 
> > Good catch. That was unintentional.
> > 
> > 
> > > Christophe
> > _______________________________________________
> > Spice-devel mailing list
> > Spice-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/spice-devel
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