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c-user: Clarify user extensions

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Sebastian Huber 2018-01-05 11:05:55 +01:00
parent ba649825d7
commit 3a594a9d06
1 changed files with 16 additions and 10 deletions
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c-user/user_extensions.rst
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@ -225,7 +225,8 @@ thread. The :c:data:`started` is a pointer to the TCB of the started thread.
It is invoked after the environment of the started thread has been loaded and the
started thread has been made ready. So, in SMP configurations, the thread may
already run on another processor before the thread start extension is actually
invoked.
invoked. Thread switch and thread begin extensions may run before or in
parallel with the thread start extension in SMP configurations.
The thread start extension is invoked in forward order with thread dispatching
disabled.
@ -254,7 +255,8 @@ reflects the previous execution context.
The thread restart extension is invoked in forward order with thread
dispatching enabled (except during system initialization). The thread life is
protected. Thread restart and delete requests issued by thread restart
extensions lead to recursion.
extensions lead to recursion. The POSIX cleanup handlers, POSIX key
destructors and thread-local object destructors run in this context.
.. index:: rtems_task_switch_extension
@ -277,7 +279,10 @@ thread. The :c:data:`heir` is a pointer to the TCB of the heir thread.
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.
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.
@ -298,12 +303,12 @@ entry function is called. The thread begin extension is defined as follows.
The :c:data:`executing` is a pointer to the TCB of the currently executing
thread. The thread begin extension executes in a normal thread context and may
allocate resources for the thread. In particular it has access to thread-local
storage of the thread.
allocate resources for the executing thread. In particular, it has access to
thread-local storage of the executing thread.
The thread begin extension is invoked in forward order with thread dispatching
enabled. The thread switch extension may be called multiple times for this
thread before the thread begin extension is invoked.
thread before or during the thread begin extension is invoked.
.. index:: rtems_task_exitted_extension
@ -344,10 +349,11 @@ extension is defined as follows.
The :c:data:`executing` is a pointer to the TCB of the currently executing
thread.
It is invoked in the context of the terminated thread right before the
thread dispatch to the heir thread. The POSIX cleanup and key destructors
execute in this context. The thread termination extension has access to
thread-local storage and thread-specific data of POSIX keys.
It is invoked in the context of the terminated thread right before the thread
dispatch to the heir thread. The POSIX cleanup handlers, POSIX key destructors
and thread-local object destructors run in this context. Depending on the
order, the thread termination extension has access to thread-local storage and
thread-specific data of POSIX keys.
The thread terminate extension is invoked in reverse order with thread
dispatching enabled. The thread life is protected. Thread restart and delete