| // Copyright 2020 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 "FreeRTOS.h" |
| #include "pw_assert/check.h" |
| #include "pw_chrono/system_clock.h" |
| #include "pw_chrono_freertos/system_clock_constants.h" |
| #include "pw_interrupt/context.h" |
| #include "semphr.h" |
| |
| using pw::chrono::SystemClock; |
| |
| namespace pw::sync { |
| namespace { |
| |
| static_assert(configUSE_COUNTING_SEMAPHORES != 0, |
| "FreeRTOS counting semaphores aren't enabled."); |
| |
| static_assert(configSUPPORT_STATIC_ALLOCATION != 0, |
| "FreeRTOS static allocations are required for this backend."); |
| |
| } // namespace |
| |
| void CountingSemaphore::release(ptrdiff_t update) { |
| if (interrupt::InInterruptContext()) { |
| for (; update > 0; --update) { |
| BaseType_t woke_higher_task = pdFALSE; |
| const BaseType_t result = xSemaphoreGiveFromISR( |
| reinterpret_cast<SemaphoreHandle_t>(&native_type_), |
| &woke_higher_task); |
| PW_DCHECK_UINT_EQ(result, pdTRUE, "Overflowed counting semaphore."); |
| portYIELD_FROM_ISR(woke_higher_task); |
| } |
| } else { // Task context |
| for (; update > 0; --update) { |
| const BaseType_t result = |
| xSemaphoreGive(reinterpret_cast<SemaphoreHandle_t>(&native_type_)); |
| PW_DCHECK_UINT_EQ(result, pdTRUE, "Overflowed counting semaphore."); |
| } |
| } |
| } |
| |
| bool CountingSemaphore::try_acquire_for(SystemClock::duration timeout) { |
| // Enforce the pw::sync::CountingSemaphore IRQ contract. |
| PW_DCHECK(!interrupt::InInterruptContext()); |
| |
| // Use non-blocking try_acquire for negative and zero length durations. |
| if (timeout <= SystemClock::duration::zero()) { |
| return try_acquire(); |
| } |
| |
| // In case the timeout is too long for us to express through the native |
| // FreeRTOS API, we repeatedly wait with shorter durations. Note that 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. However, this also means |
| // that the loop must ensure that timeout + 1 is less than the max timeout. |
| constexpr SystemClock::duration kMaxTimeoutMinusOne = |
| pw::chrono::freertos::kMaxTimeout - SystemClock::duration(1); |
| while (timeout > kMaxTimeoutMinusOne) { |
| if (xSemaphoreTake(reinterpret_cast<SemaphoreHandle_t>(&native_type_), |
| static_cast<TickType_t>(kMaxTimeoutMinusOne.count())) == |
| pdTRUE) { |
| return true; |
| } |
| timeout -= kMaxTimeoutMinusOne; |
| } |
| // 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. |
| return xSemaphoreTake(reinterpret_cast<SemaphoreHandle_t>(&native_type_), |
| static_cast<TickType_t>(timeout.count() + 1)) == pdTRUE; |
| } |
| |
| } // namespace pw::sync |