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

[Hirokazu Honda]

Hi Laurent, thank you for the patch.

On Mon, May 24, 2021 at 11:58 AM Umang Jain <umang.jain at ideasonboard.com>
wrote:

> Hi Laurent
>
> Thanks for the patch
>
> On 5/23/21 8:01 AM, 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: Umang Jain <umang.jain at ideasonboard.com>
>

Reviewed-by: Hirokazu Honda <hiroh at chromium.org>


> > ---
> >   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)
> >   {
>
>
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