[Spice-devel] [spice-gtk v2] usbredir: fix deadlock on error

[Victor Toso]

On Tue, Jun 20, 2017 at 01:10:43PM +0200, Victor Toso wrote:
> From: leaboy <wlbleaboy at 126.com>
> 
> The current code deadlocks when a USB error occurs, releasing the
> channel lock before the idle is called fixes this problem.
> 
> More specifically when an error occurs, we queue a call to device_error
> in an idle, and switch to the main context. The device_error() calls
> spice_usbredir_channel_disconnect_device() which needs the channel to be
> unlocked as it calls spice_usbredir_channel_lock().
> 
> Examples:
> - Redirect USB Storage device to the guest and copy some big file. While
>   copy is ongoing, unplug the USB Storage from the client machine;
> - Unplug the usb device from the client machine while the USB Storage
>   device is being identified in the guest.
> - With the auto-redirection option enabled, plug and unplug the USB
>   Storage Device frequently.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1353528

Btw, I'm guessing that this is the same bug.

> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>  src/channel-usbredir.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/src/channel-usbredir.c b/src/channel-usbredir.c
> index fef62ce..1f791bc 100644
> --- a/src/channel-usbredir.c
> +++ b/src/channel-usbredir.c
> @@ -927,15 +927,16 @@ static void usbredir_handle_msg(SpiceChannel *c, SpiceMsgIn *in)
>          err_data.caller = coroutine_self();
>          err_data.spice_device = g_boxed_copy(spice_usb_device_get_type(), spice_device);
>          err_data.error = err;
> +        spice_usbredir_channel_unlock(channel);
>          g_idle_add(device_error, &err_data);
>          coroutine_yield(NULL);
>  
>          g_boxed_free(spice_usb_device_get_type(), err_data.spice_device);
>  
>          g_error_free(err);
> +    } else {
> +        spice_usbredir_channel_unlock(channel);
>      }
> -
> -    spice_usbredir_channel_unlock(channel);
>  }
>  
>  #endif /* USE_USBREDIR */
> -- 
> 2.13.0
> 
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