1 // Copyright 2021 The Pigweed Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not 4 // use this file except in compliance with the License. You may obtain a copy of 5 // the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12 // License for the specific language governing permissions and limitations under 13 // the License. 14 #pragma once 15 16 #include <optional> 17 18 #include "pw_assert/assert.h" 19 #include "pw_thread/thread.h" 20 #include "pw_thread_threadx/config.h" 21 #include "pw_thread_threadx/context.h" 22 #include "tx_api.h" 23 24 namespace pw::thread::threadx { 25 26 // pw::thread::Options for ThreadX. 27 // 28 // Example usage: 29 // 30 // // Uses the default priority and time slice interval (which may be 31 // // disabled), but specifies a custom name and pre-allocated context. 32 // // Note that the preemption threshold is disabled by default. 33 // pw::thread::Thread example_thread( 34 // pw::thread::threadx::Options() 35 // .set_name("example_thread"), 36 // .set_context(example_thread_context), 37 // example_thread_function); 38 // 39 // // Specifies the name, priority, time slice interval, and pre-allocated 40 // // context, but does not use a preemption threshold. 41 // pw::thread::Thread static_example_thread( 42 // pw::thread::threadx::Options() 43 // .set_name("static_example_thread") 44 // .set_priority(kFooPriority) 45 // .set_time_slice_interval(1) 46 // .set_context(example_thread_context), 47 // example_thread_function); 48 // 49 class Options : public thread::Options { 50 public: Options()51 constexpr Options() {} 52 constexpr Options(const Options&) = default; 53 constexpr Options(Options&&) = default; 54 55 // Sets the name for the ThreadX thread, note that this will be deep copied 56 // into the context and may be truncated based on 57 // PW_THREAD_THREADX_CONFIG_MAX_THREAD_NAME_LEN. set_name(const char * name)58 constexpr Options& set_name(const char* name) { 59 name_ = name; 60 return *this; 61 } 62 63 // Sets the priority for the ThreadX thread from 0 through 31, where a value 64 // of 0 represents the highest priority, see ThreadX tx_thread_create for 65 // more detail. 66 // 67 // Precondition: priority <= PW_THREAD_THREADX_CONFIG_MIN_PRIORITY set_priority(UINT priority)68 constexpr Options& set_priority(UINT priority) { 69 PW_DASSERT(priority <= PW_THREAD_THREADX_CONFIG_MIN_PRIORITY); 70 priority_ = priority; 71 return *this; 72 } 73 74 // Optionally sets the preemption threshold for the ThreadX thread from 0 75 // through 31. 76 // 77 // Only priorities higher than this level (i.e. lower number) are allowed to 78 // preempt this thread. In other words this allows the thread to specify the 79 // priority ceiling for disabling preemption. Threads that have a higher 80 // priority than the ceiling are still allowed to preempt while those with 81 // less than the ceiling are not allowed to preempt. 82 // 83 // Not setting the preemption threshold or explicitly specifying a value 84 // equal to the priority disables preemption threshold. 85 // 86 // Time slicing is disabled while the preemption threshold is enabled, i.e. 87 // not equal to the priority, even if a time slice interval was specified. 88 // 89 // The preemption threshold can be adjusted at run time, this only sets the 90 // initial threshold. 91 // 92 // Precondition: preemption_threshold <= priority set_preemption_threshold(UINT preemption_threshold)93 constexpr Options& set_preemption_threshold(UINT preemption_threshold) { 94 PW_DASSERT(preemption_threshold < PW_THREAD_THREADX_CONFIG_MIN_PRIORITY); 95 possible_preemption_threshold_ = preemption_threshold; 96 return *this; 97 } 98 99 // Sets the number of ticks this thread is allowed to run before other ready 100 // threads of the same priority are given a chance to run. 101 // 102 // Time slicing is disabled while the preemption threshold is enabled, i.e. 103 // not equal to the priority, even if a time slice interval was specified. 104 // 105 // A value of TX_NO_TIME_SLICE (a value of 0) disables time-slicing of this 106 // thread. 107 // 108 // Using time slicing results in a slight amount of system overhead, threads 109 // with a unique priority should consider TX_NO_TIME_SLICE. set_time_slice_interval(ULONG time_slice_interval)110 constexpr Options& set_time_slice_interval(ULONG time_slice_interval) { 111 time_slice_interval_ = time_slice_interval; 112 return *this; 113 } 114 115 // Set the pre-allocated context (all memory needed to run a thread). Note 116 // that this is required for this thread creation backend! The Context can 117 // either be constructed with an externally provided span<ULONG> stack 118 // or the templated form of ContextWihtStack<kStackSizeWords> can be used. set_context(Context & context)119 constexpr Options& set_context(Context& context) { 120 context_ = &context; 121 return *this; 122 } 123 124 private: 125 friend thread::Thread; 126 // Note that the default name may end up truncated due to 127 // PW_THREAD_THREADX_CONFIG_MAX_THREAD_NAME_LEN. 128 static constexpr char kDefaultName[] = "pw::Thread"; 129 name()130 const char* name() const { return name_; } priority()131 UINT priority() const { return priority_; } preemption_threshold()132 UINT preemption_threshold() const { 133 return possible_preemption_threshold_.value_or(priority_); 134 } time_slice_interval()135 ULONG time_slice_interval() const { return time_slice_interval_; } context()136 Context* context() const { return context_; } 137 138 const char* name_ = kDefaultName; 139 UINT priority_ = config::kDefaultPriority; 140 // A default value cannot be used for the preemption threshold as it would 141 // have to be based on the selected priority. 142 std::optional<UINT> possible_preemption_threshold_ = std::nullopt; 143 ULONG time_slice_interval_ = config::kDefaultTimeSliceInterval; 144 Context* context_ = nullptr; 145 }; 146 147 } // namespace pw::thread::threadx 148