[PATCH xserver] os: Lock input while messing with input device list

[Peter Hutterer]

On Tue, May 31, 2016 at 09:17:39AM -0700, Keith Packard wrote:
> The list of input devices may be changed by hotplugging while the
> server is active, and those changes may come from either the main
> thread or the input thread. That means the list of input devices needs
> to be protected by a mutex.
> 
> This prevents input drivers from receiving I/O ready callbacks after
> removing a device.
> 
> Signed-off-by: Keith Packard <keithp at keithp.com>

Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>

Cheers,
   Peter
> ---
>  os/inputthread.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/os/inputthread.c b/os/inputthread.c
> index 390b66b..40a0443 100644
> --- a/os/inputthread.c
> +++ b/os/inputthread.c
> @@ -197,12 +197,14 @@ InputThreadRegisterDev(int fd,
>      dev->readInputProc = readInputProc;
>      dev->readInputArgs = readInputArgs;
>  
> +    input_lock();
>      xorg_list_add(&dev->node, &inputThreadInfo->devs);
>  
>      FD_SET(fd, &inputThreadInfo->fds);
>  
>      InputThreadFillPipe(hotplugPipeWrite);
>      DebugF("input-thread: registered device %d\n", fd);
> +    input_unlock();
>  
>      return 1;
>  }
> @@ -228,6 +230,7 @@ InputThreadUnregisterDev(int fd)
>          return 1;
>      }
>  
> +    input_lock();
>      xorg_list_for_each_entry(dev, &inputThreadInfo->devs, node)
>          if (dev->fd == fd) {
>              found_device = TRUE;
> @@ -235,12 +238,17 @@ InputThreadUnregisterDev(int fd)
>          }
>  
>      /* fd didn't match any registered device. */
> -    if (!found_device)
> +    if (!found_device) {
> +        input_unlock();
>          return 0;
> +    }
>  
>      xorg_list_del(&dev->node);
>  
>      FD_CLR(fd, &inputThreadInfo->fds);
> +
> +    input_unlock();
> +
>      free(dev);
>  
>      InputThreadFillPipe(hotplugPipeWrite);
> @@ -292,14 +300,14 @@ InputThreadDoWork(void *arg)
>  
>          DebugF("input-thread: %s generating events\n", __func__);
>  
> +        input_lock();
>          /* Call the device drivers to generate input events for us */
>          xorg_list_for_each_entry_safe(dev, next, &inputThreadInfo->devs, node) {
>              if (FD_ISSET(dev->fd, &readyFds) && dev->readInputProc) {
> -                input_lock();
>                  dev->readInputProc(dev->fd, X_NOTIFY_READ, dev->readInputArgs);
> -                input_unlock();
>              }
>          }
> +        input_unlock();
>  
>          /* Kick main thread to process the generated input events and drain
>           * events from hotplug pipe */
> -- 
> 2.8.1
>