Ewout van Bekkum | 8b72a57 | 2021-03-09 08:53:39 -0800 | [diff] [blame] | 1 | .. _module-pw_thread_embos: |
| 2 | |
Ewout van Bekkum | 6e5d43e | 2021-05-06 15:29:44 -0700 | [diff] [blame] | 3 | =============== |
Ewout van Bekkum | 8b72a57 | 2021-03-09 08:53:39 -0800 | [diff] [blame] | 4 | pw_thread_embos |
Ewout van Bekkum | 6e5d43e | 2021-05-06 15:29:44 -0700 | [diff] [blame] | 5 | =============== |
| 6 | This is a set of backends for pw_thread based on embOS v4. |
Ewout van Bekkum | 8b72a57 | 2021-03-09 08:53:39 -0800 | [diff] [blame] | 7 | |
Ewout van Bekkum | 6e5d43e | 2021-05-06 15:29:44 -0700 | [diff] [blame] | 8 | .. contents:: |
| 9 | :local: |
| 10 | :depth: 1 |
| 11 | |
| 12 | .. Warning:: |
| 13 | This module is still under construction, the API is not yet stable. |
| 14 | |
| 15 | ----------------------- |
| 16 | Thread Creation Backend |
| 17 | ----------------------- |
| 18 | A backend or ``pw::thread::Thread`` is offered using ``OS_CreateTaskEx()``. |
| 19 | Optional joining support is enabled via an ``OS_EVENT`` in each thread's |
| 20 | context. |
| 21 | |
| 22 | This backend permits users to start threads where contexts must be explicitly |
| 23 | allocated and passed in as an option. As a quick example, a detached thread |
| 24 | can be created as follows: |
| 25 | |
| 26 | .. code-block:: cpp |
| 27 | |
| 28 | #include "pw_thread/detached_thread.h" |
| 29 | #include "pw_thread_embos/context.h" |
| 30 | #include "pw_thread_embos/options.h" |
| 31 | #include "RTOS.h" // For the embOS types. |
| 32 | |
| 33 | pw::thread::embos::ContextWithStack<42> example_thread_context; |
| 34 | void StartExampleThread() { |
| 35 | pw::thread::DetachedThread( |
| 36 | pw::thread::embos::Options() |
| 37 | .set_name("static_example_thread") |
| 38 | .set_priority(kFooPriority) |
| 39 | .set_time_slice_interval(kFooTimeSliceInterval) |
| 40 | .set_context(example_thread_context), |
| 41 | example_thread_function) |
| 42 | } |
| 43 | |
| 44 | |
| 45 | Module Configuration Options |
| 46 | ============================ |
| 47 | The following configurations can be adjusted via compile-time configuration of |
| 48 | this module, see the |
| 49 | :ref:`module documentation <module-structure-compile-time-configuration>` for |
| 50 | more details. |
| 51 | |
| 52 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_JOINING_ENABLED |
| 53 | |
| 54 | Whether thread joining is enabled. By default this is disabled. |
| 55 | |
| 56 | We suggest only enabling this when thread joining is required to minimize |
| 57 | the RAM and ROM cost of threads. |
| 58 | |
| 59 | Enabling this grows the RAM footprint of every pw::thread::Thread as it adds |
| 60 | an OS_EVENT to every thread's pw::thread::embos::Context. In addition, there |
| 61 | is a minute ROM cost to construct and destroy this added object. |
| 62 | |
| 63 | PW_THREAD_JOINING_ENABLED gets set to this value. |
| 64 | |
| 65 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_MINIMUM_STACK_SIZE_WORDS |
| 66 | |
| 67 | The minimum stack size in words. By default this uses Segger's recommendation |
| 68 | of 68 bytes. |
| 69 | |
| 70 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_DEFAULT_STACK_SIZE_WORDS |
| 71 | |
| 72 | The default stack size in words. By default this uses Segger's recommendation |
| 73 | of 256 bytes to start. |
| 74 | |
| 75 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_MAX_THREAD_NAME_LEN |
| 76 | |
| 77 | The maximum length of a thread's name, not including null termination. By |
| 78 | default this is arbitrarily set to 15. This results in an array of characters |
| 79 | which is this length + 1 bytes in every ``pw::thread::Thread``'s context. |
| 80 | |
| 81 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_MIN_PRIORITY |
| 82 | |
| 83 | The minimum priority level, this is normally 1, since 0 is not a valid |
| 84 | priority level. |
| 85 | |
| 86 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_DEFAULT_PRIORITY |
| 87 | |
| 88 | The default priority level. By default this uses the minimal embOS priority. |
| 89 | |
| 90 | .. c:macro:: PW_THREAD_EMBOS_CONFIG_DEFAULT_TIME_SLICE_INTERVAL |
| 91 | |
| 92 | The round robin time slice tick interval for threads at the same priority. |
| 93 | By default this is set to 2 ticks based on the embOS default. |
| 94 | |
| 95 | |
| 96 | embOS Thread Options |
| 97 | ==================== |
| 98 | .. cpp:class:: pw::thread::embos::Options |
| 99 | |
| 100 | .. cpp:function:: set_name(const char* name) |
| 101 | |
| 102 | Sets the name for the embOS task, this is optional. |
| 103 | Note that this will be deep copied into the context and may be truncated |
| 104 | based on ``PW_THREAD_EMBOS_CONFIG_MAX_THREAD_NAME_LEN``. |
| 105 | |
| 106 | .. cpp:function:: set_priority(OS_PRIO priority) |
| 107 | |
| 108 | Sets the priority for the embOS task. Higher values are higher priority, |
| 109 | see embOS OS_CreateTaskEx for more detail. |
| 110 | Precondition: This must be >= ``PW_THREAD_EMBOS_CONFIG_MIN_PRIORITY``. |
| 111 | |
| 112 | .. cpp:function:: set_time_slice_interval(OS_UINT time_slice_interval) |
| 113 | |
| 114 | Sets the number of ticks this thread is allowed to run before other ready |
| 115 | threads of the same priority are given a chance to run. |
| 116 | |
| 117 | A value of 0 disables time-slicing of this thread. |
| 118 | |
| 119 | Precondition: This must be <= 255 ticks. |
| 120 | |
| 121 | .. cpp:function:: set_context(pw::thread::embos::Context& context) |
| 122 | |
| 123 | Set the pre-allocated context (all memory needed to run a thread). Note that |
| 124 | this is required for this thread creation backend! The ``Context`` can |
| 125 | either be constructed with an externally provided ``std::span<OS_UINT>`` |
| 126 | stack or the templated form of ``ContextWithStack<kStackSizeWords>`` can |
| 127 | be used. |
| 128 | |
| 129 | |
| 130 | ----------------------------- |
| 131 | Thread Identification Backend |
| 132 | ----------------------------- |
| 133 | A backend for ``pw::thread::Id`` and ``pw::thread::get_id()`` is offerred using |
| 134 | ``OS_GetTaskID()``. It uses ``DASSERT`` to ensure that the scheduler has started |
| 135 | via ``OS_IsRunning()``. |
| 136 | |
| 137 | -------------------- |
| 138 | Thread Sleep Backend |
| 139 | -------------------- |
| 140 | A backend for ``pw::thread::sleep_for()`` and ``pw::thread::sleep_until()`` is |
| 141 | offerred using ``OS_Delay()`` if the duration is at least one tick, else |
| 142 | ``OS_Yield()`` is used. It uses ``pw::this_thread::get_id() != thread::Id()`` to |
| 143 | ensure it invoked only from a thread. |
| 144 | |
| 145 | -------------------- |
| 146 | Thread Yield Backend |
| 147 | -------------------- |
| 148 | A backend for ``pw::thread::yield()`` is offered using via ``OS_Yield()``. |
| 149 | It uses ``pw::this_thread::get_id() != thread::Id()`` to ensure it invoked only |
| 150 | from a thread. |