1 // Copyright 2020 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 15 #include "pw_thread/sleep.h" 16 17 #include <algorithm> 18 19 #include "FreeRTOS.h" 20 #include "pw_assert/check.h" 21 #include "pw_chrono/system_clock.h" 22 #include "pw_chrono_freertos/system_clock_constants.h" 23 #include "pw_thread/thread.h" 24 #include "task.h" 25 26 using pw::chrono::SystemClock; 27 28 namespace pw::this_thread { 29 sleep_for(SystemClock::duration sleep_duration)30void sleep_for(SystemClock::duration sleep_duration) { 31 // Ensure this is being called by a thread. 32 PW_DCHECK(get_id() != Thread::id()); 33 34 // Yield for negative and zero length durations. 35 if (sleep_duration <= SystemClock::duration::zero()) { 36 taskYIELD(); 37 return; 38 } 39 40 // In case the timeout is too long for us to express through the native 41 // FreeRTOS API, we repeatedly wait with shorter durations. Note that on a 42 // tick based kernel we cannot tell how far along we are on the current tick, 43 // ergo we add one whole tick to the final duration. However, this also means 44 // that the loop must ensure that timeout + 1 is less than the max timeout. 45 constexpr SystemClock::duration kMaxTimeoutMinusOne = 46 pw::chrono::freertos::kMaxTimeout - SystemClock::duration(1); 47 while (sleep_duration > kMaxTimeoutMinusOne) { 48 vTaskDelay(static_cast<TickType_t>(kMaxTimeoutMinusOne.count())); 49 sleep_duration -= kMaxTimeoutMinusOne; 50 } 51 // On a tick based kernel we cannot tell how far along we are on the current 52 // tick, ergo we add one whole tick to the final duration. 53 vTaskDelay(static_cast<TickType_t>(sleep_duration.count() + 1)); 54 } 55 56 } // namespace pw::this_thread 57