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