[libcamera-devel] [PATCH 1/4] libcamera: thread: Document dispatchMessages() thread-safety requirements

[Niklas Söderlund]

Hi Laurent,

Thanks for your work.

On 2021-05-23 05:31:52 +0300, Laurent Pinchart wrote:
> The Thread class is incorrectly documented as thread-safe, as the
> dispatchMessages() function isn't thread-safe. Fix the documentation by
> tagging individual functions as thread-safe as appropriate.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>

> ---
>  src/libcamera/thread.cpp | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/thread.cpp b/src/libcamera/thread.cpp
> index 198670de33a2..285b808332e8 100644
> --- a/src/libcamera/thread.cpp
> +++ b/src/libcamera/thread.cpp
> @@ -229,8 +229,6 @@ ThreadData *ThreadData::current()
>   * called. The event loop dispatches events (messages, notifiers and timers)
>   * sent to the objects living in the thread. This behaviour can be modified by
>   * overriding the run() function.
> - *
> - * \context This class is \threadsafe.
>   */
>  
>  /**
> @@ -361,6 +359,8 @@ void Thread::finishThread()
>   *
>   * Calling exit() on a thread that reimplements the run() method and doesn't
>   * call exec() will likely have no effect.
> + *
> + * \context This function is \threadsafe.
>   */
>  void Thread::exit(int code)
>  {
> @@ -383,6 +383,8 @@ void Thread::exit(int code)
>   * utils::duration::max(), the wait never times out. If the thread is not
>   * running the function returns immediately.
>   *
> + * \context This function is \threadsafe.
> + *
>   * \return True if the thread has finished, or false if the wait timed out
>   */
>  bool Thread::wait(utils::duration duration)
> @@ -412,6 +414,8 @@ bool Thread::wait(utils::duration duration)
>   * started. This method guarantees that it returns true after the start()
>   * method returns, and false after the wait() method returns.
>   *
> + * \context This function is \threadsafe.
> + *
>   * \return True if the thread is running, false otherwise
>   */
>  bool Thread::isRunning()
> @@ -427,6 +431,7 @@ bool Thread::isRunning()
>  
>  /**
>   * \brief Retrieve the Thread instance for the current thread
> + * \context This function is \threadsafe.
>   * \return The Thread instance for the current thread
>   */
>  Thread *Thread::current()
> @@ -441,6 +446,8 @@ Thread *Thread::current()
>   * The thread ID corresponds to the Linux thread ID (TID) as returned by the
>   * gettid system call.
>   *
> + * \context This function is \threadsafe.
> + *
>   * \return The ID of the current thread
>   */
>  pid_t Thread::currentId()
> @@ -455,6 +462,8 @@ pid_t Thread::currentId()
>   * This function retrieves the internal event dispatcher for the thread. The
>   * returned event dispatcher is valid until the thread is destroyed.
>   *
> + * \context This function is \threadsafe.
> + *
>   * \return Pointer to the event dispatcher
>   */
>  EventDispatcher *Thread::eventDispatcher()
> @@ -544,6 +553,10 @@ void Thread::removeMessages(Object *receiver)
>   * This function immediately dispatches all the messages previously posted for
>   * this thread with postMessage() that match the message \a type. If the \a type
>   * is Message::Type::None, all messages are dispatched.
> + *
> + * Messages shall only be dispatched from the current thread, typically within
> + * the thread from the run() function. Calling this function outside of the
> + * thread results in undefined behaviour.
>   */
>  void Thread::dispatchMessages(Message::Type type)
>  {
> -- 
> Regards,
> 
> Laurent Pinchart
> 

-- 
Regards,
Niklas Söderlund