On Tue, Mar 3, 2020 at 12:03 AM Sebastian Huber <sebastian.hu...@embedded-brains.de> wrote: > > Close #3885. > --- > c-user/symmetric_multiprocessing_services.rst | 2 ++ > c-user/user_extensions.rst | 40 > ++++++++++++++++++--------- > 2 files changed, 29 insertions(+), 13 deletions(-) > > diff --git a/c-user/symmetric_multiprocessing_services.rst > b/c-user/symmetric_multiprocessing_services.rst > index 337de98..acfee56 100644 > --- a/c-user/symmetric_multiprocessing_services.rst > +++ b/c-user/symmetric_multiprocessing_services.rst > @@ -683,6 +683,8 @@ The withdraw operation takes away scheduler nodes once > the thread is no longer > allowed to use them, e.g. it released a mutex. The availability of scheduler > nodes for a thread is controlled by the thread queues. > > +.. _SMPThreadDispatchDetails: > + > Thread Dispatch Details > ----------------------- > > diff --git a/c-user/user_extensions.rst b/c-user/user_extensions.rst > index 0840f65..7edbea5 100644 > --- a/c-user/user_extensions.rst > +++ b/c-user/user_extensions.rst > @@ -261,9 +261,7 @@ destructors and thread-local object destructors run in > this context. > Thread Switch Extension > ----------------------- > > -The thread switch extension is invoked before the context switch from the > -currently executing thread to the heir thread. The thread switch extension > is > -defined as follows. > +The thread switch extension is defined as follows. > > .. code-block:: c > > @@ -272,18 +270,34 @@ defined as follows. > rtems_tcb *heir > ); > > -The :c:data:`executing` is a pointer to the TCB of the currently executing > -thread. The :c:data:`heir` is a pointer to the TCB of the heir thread. > +The invocation conditions of the thread switch extension depend on whether > RTEMS > +was configured for uniprocessor or SMP systems. A user must pay attention to > +the differences to correctly implement a thread switch extension. > + > +In uniprocessor configurations, the thread switch extension is invoked before > +the context switch from the currently executing thread to the heir thread. > The > +:c:data:`executing` is a pointer to the TCB of the currently executing > thread. > +The :c:data:`heir` is a pointer to the TCB of the heir thread. The context > +switch initiated through the multitasking start is not covered by the thread > +switch extension. > + > +In SMP configurations, the thread switch extension is invoked after the > context > +switch to the new executing thread (previous heir thread). The > +:c:data:`executing` is a pointer to the TCB of the previously executing > thread. > +Despite the name, this is not the currently executing thread. The > +:c:data:`heir` is a pointer to the TCB of the newly executing thread. This > is > +the executing thread. The context switches initiated through the > multitasking Although I understand it, I think you might put "the currently executing thread" here as well.
Rest looks good. > +start are covered by the thread switch extension. The reason for the > +differences to uniprocessor configurations is that the context switch may > update > +the heir thread of the processor, see :ref:`SMPThreadDispatchDetails`. The > +thread switch extensions are invoked with disabled interrupts and with > ownership > +of a per-processor SMP lock. Thread switch extensions may run in parallel on > +multiple processors. It is recommended to use thread-local or per-processor > +data structures for thread switch extensions. A global SMP lock should be > +avoided for performance reasons. > > The thread switch extension is invoked in forward order with thread > dispatching > -disabled. In SMP configurations, interrupts are disabled and the > per-processor > -SMP lock is owned. Thread switch extensions may run in parallel on multiple > -processors. It is recommended to use thread-local or per-processor data > -structures in SMP configurations for thread switch extensions. A global SMP > -lock should be avoided for performance reasons. > - > -The context switches initiated through the multitasking start are not covered > -by the thread switch extension. > +disabled. > > .. index:: rtems_task_begin_extension > > -- > 2.16.4 > > _______________________________________________ > devel mailing list > devel@rtems.org > http://lists.rtems.org/mailman/listinfo/devel _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
