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doc: Adjust pthread description

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Refer to the latest code, modified the description of pthread.

Signed-off-by: anlan_cs <vic.lan@pica8.com>
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anlan_cs 2023-06-12 12:56:24 +08:00
parent e631541b68
commit eb678efed8
1 changed files with 6 additions and 5 deletions
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11
doc/developer/process-architecture.rst
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@ -210,7 +210,8 @@ Kernel Thread Wrapper
The basis for the integration of pthreads and the event system is a lightweight
wrapper for both systems implemented in :file:`lib/frr_pthread.[ch]`. The
header provides a core datastructure, ``struct frr_pthread``, that encapsulates
structures from both POSIX threads and :file:`thread.[ch]`. In particular, this
structures from both POSIX threads and :file:`event.c`, :file:`frrevent.h`.
In particular, this
datastructure has a pointer to a ``threadmaster`` that runs within the pthread.
It also has fields for a name as well as start and stop functions that have
signatures similar to the POSIX arguments for ``pthread_create()``.
@ -218,18 +219,18 @@ signatures similar to the POSIX arguments for ``pthread_create()``.
Calling ``frr_pthread_new()`` creates and registers a new ``frr_pthread``. The
returned structure has a pre-initialized ``threadmaster``, and its ``start``
and ``stop`` functions are initialized to defaults that will run a basic event
loop with the given threadmaster. Calling ``frr_pthread_run`` starts the thread
loop with the given threadmaster. Calling ``frr_pthread_run()`` starts the thread
with the ``start`` function. From there, the model is the same as the regular
event model. To schedule tasks on a particular pthread, simply use the regular
:file:`thread.c` functions as usual and provide the ``threadmaster`` pointed to
:file:`event.c` functions as usual and provide the ``threadmaster`` pointed to
from the ``frr_pthread``. As part of implementing the wrapper, the
:file:`thread.c` functions were made thread-safe. Consequently, it is safe to
:file:`event.c` functions were made thread-safe. Consequently, it is safe to
schedule events on a ``threadmaster`` belonging both to the calling thread as
well as *any other pthread*. This serves as the basis for inter-thread
communication and boils down to a slightly more complicated method of message
passing, where the messages are the regular task events as used in the
event-driven model. The only difference is thread cancellation, which requires
calling ``event_cancel_async()`` instead of ``event_cancel`` to cancel a task
calling ``event_cancel_async()`` instead of ``event_cancel()`` to cancel a task
currently scheduled on a ``threadmaster`` belonging to a different pthread.
This is necessary to avoid race conditions in the specific case where one
pthread wants to guarantee that a task on another pthread is cancelled before