Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 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_sync/counting_semaphore.h" |
| 16 | |
| 17 | #include <algorithm> |
| 18 | |
| 19 | #include "RTOS.h" |
Wyatt Hepler | f298de4 | 2021-03-19 15:06:36 -0700 | [diff] [blame] | 20 | #include "pw_assert/check.h" |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 21 | #include "pw_chrono/system_clock.h" |
| 22 | #include "pw_chrono_embos/system_clock_constants.h" |
| 23 | #include "pw_interrupt/context.h" |
| 24 | |
| 25 | using pw::chrono::SystemClock; |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 26 | |
| 27 | namespace pw::sync { |
| 28 | |
| 29 | void CountingSemaphore::release(ptrdiff_t update) { |
| 30 | for (; update > 0; --update) { |
| 31 | // There is no API to atomically detect overflow, however debug builds of |
| 32 | // embOS call OS_Error() internally when overflow is detected for the native |
| 33 | // token representation. Rather than enter a critical section both due to |
| 34 | // cost and potential direct use of the native handle, a lazy check is used |
| 35 | // for debug builds which may not trigger on the initial overflow. |
| 36 | PW_DCHECK_UINT_LE(OS_GetCSemaValue(&native_type_), |
| 37 | CountingSemaphore::max(), |
| 38 | "Overflowed counting semaphore."); |
| 39 | OS_SignalCSema(&native_type_); |
| 40 | } |
| 41 | } |
| 42 | |
| 43 | bool CountingSemaphore::try_acquire_for(SystemClock::duration for_at_least) { |
| 44 | PW_DCHECK(!interrupt::InInterruptContext()); |
| 45 | |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 46 | // Use non-blocking try_acquire for negative and zero length durations. |
| 47 | if (for_at_least <= SystemClock::duration::zero()) { |
| 48 | return try_acquire(); |
| 49 | } |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 50 | |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 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 | constexpr SystemClock::duration kMaxTimeoutMinusOne = |
| 54 | pw::chrono::embos::kMaxTimeout - SystemClock::duration(1); |
| 55 | while (for_at_least > kMaxTimeoutMinusOne) { |
| 56 | if (OS_WaitCSemaTimed(&native_type_, |
| 57 | static_cast<OS_TIME>(kMaxTimeoutMinusOne.count()))) { |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 58 | return true; |
| 59 | } |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 60 | for_at_least -= kMaxTimeoutMinusOne; |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 61 | } |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 62 | return OS_WaitCSemaTimed(&native_type_, |
| 63 | static_cast<OS_TIME>(for_at_least.count() + 1)); |
Ewout van Bekkum | e11ed69 | 2021-03-05 11:02:18 -0800 | [diff] [blame] | 64 | } |
| 65 | |
| 66 | } // namespace pw::sync |