| // Copyright 2021 The Pigweed Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| // use this file except in compliance with the License. You may obtain a copy of |
| // the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| // License for the specific language governing permissions and limitations under |
| // the License. |
| |
| #include "pw_sync/counting_semaphore.h" |
| |
| #include <algorithm> |
| |
| #include "RTOS.h" |
| #include "pw_assert/check.h" |
| #include "pw_chrono/system_clock.h" |
| #include "pw_chrono_embos/system_clock_constants.h" |
| #include "pw_interrupt/context.h" |
| |
| using pw::chrono::SystemClock; |
| |
| namespace pw::sync { |
| |
| void CountingSemaphore::release(ptrdiff_t update) { |
| for (; update > 0; --update) { |
| // There is no API to atomically detect overflow, however debug builds of |
| // embOS call OS_Error() internally when overflow is detected for the native |
| // token representation. Rather than enter a critical section both due to |
| // cost and potential direct use of the native handle, a lazy check is used |
| // for debug builds which may not trigger on the initial overflow. |
| PW_DCHECK_UINT_LE(OS_GetCSemaValue(&native_type_), |
| CountingSemaphore::max(), |
| "Overflowed counting semaphore."); |
| OS_SignalCSema(&native_type_); |
| } |
| } |
| |
| bool CountingSemaphore::try_acquire_for(SystemClock::duration for_at_least) { |
| PW_DCHECK(!interrupt::InInterruptContext()); |
| |
| // Use non-blocking try_acquire for negative and zero length durations. |
| if (for_at_least <= SystemClock::duration::zero()) { |
| return try_acquire(); |
| } |
| |
| // On a tick based kernel we cannot tell how far along we are on the current |
| // tick, ergo we add one whole tick to the final duration. |
| constexpr SystemClock::duration kMaxTimeoutMinusOne = |
| pw::chrono::embos::kMaxTimeout - SystemClock::duration(1); |
| while (for_at_least > kMaxTimeoutMinusOne) { |
| if (OS_WaitCSemaTimed(&native_type_, |
| static_cast<OS_TIME>(kMaxTimeoutMinusOne.count()))) { |
| return true; |
| } |
| for_at_least -= kMaxTimeoutMinusOne; |
| } |
| return OS_WaitCSemaTimed(&native_type_, |
| static_cast<OS_TIME>(for_at_least.count() + 1)); |
| } |
| |
| } // namespace pw::sync |