Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -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 | |
Ewout van Bekkum | 6f5b8fb | 2021-04-06 16:15:22 -0700 | [diff] [blame] | 15 | #include "pw_sync/timed_mutex.h" |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 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 | 99a6c20 | 2021-03-05 08:44:29 -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 | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 26 | |
| 27 | namespace pw::sync { |
| 28 | |
Ewout van Bekkum | 5ff8cc5 | 2021-09-07 15:46:36 -0700 | [diff] [blame] | 29 | bool TimedMutex::try_lock_for(SystemClock::duration timeout) { |
Ewout van Bekkum | a6642d7 | 2021-11-05 09:43:14 -0700 | [diff] [blame] | 30 | // Enforce the pw::sync::TimedMutex IRQ contract. |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 31 | PW_DCHECK(!interrupt::InInterruptContext()); |
| 32 | |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 33 | // Use non-blocking try_lock for negative and zero length durations. |
Ewout van Bekkum | 5ff8cc5 | 2021-09-07 15:46:36 -0700 | [diff] [blame] | 34 | if (timeout <= SystemClock::duration::zero()) { |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 35 | return try_lock(); |
| 36 | } |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 37 | |
Ewout van Bekkum | a6642d7 | 2021-11-05 09:43:14 -0700 | [diff] [blame] | 38 | // In case the timeout is too long for us to express through the native |
| 39 | // embOS API, we repeatedly wait with shorter durations. Note that on a tick |
| 40 | // based kernel we cannot tell how far along we are on the current tick, ergo |
| 41 | // we add one whole tick to the final duration. However, this also means that |
| 42 | // the loop must ensure that timeout + 1 is less than the max timeout. |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 43 | constexpr SystemClock::duration kMaxTimeoutMinusOne = |
| 44 | pw::chrono::embos::kMaxTimeout - SystemClock::duration(1); |
Ewout van Bekkum | 5ff8cc5 | 2021-09-07 15:46:36 -0700 | [diff] [blame] | 45 | while (timeout > kMaxTimeoutMinusOne) { |
Ewout van Bekkum | 86c2547 | 2021-03-11 08:30:39 -0800 | [diff] [blame] | 46 | const int lock_count = OS_UseTimed( |
Ewout van Bekkum | 6f5b8fb | 2021-04-06 16:15:22 -0700 | [diff] [blame] | 47 | &native_handle(), static_cast<OS_TIME>(kMaxTimeoutMinusOne.count())); |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 48 | if (lock_count != 0) { |
Ewout van Bekkum | d5f83f9 | 2021-11-05 12:31:28 -0700 | [diff] [blame] | 49 | PW_DCHECK_UINT_EQ(1, lock_count, "Recursive locking is not permitted"); |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 50 | return true; |
| 51 | } |
Ewout van Bekkum | 5ff8cc5 | 2021-09-07 15:46:36 -0700 | [diff] [blame] | 52 | timeout -= kMaxTimeoutMinusOne; |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 53 | } |
Ewout van Bekkum | a6642d7 | 2021-11-05 09:43:14 -0700 | [diff] [blame] | 54 | // On a tick based kernel we cannot tell how far along we are on the current |
| 55 | // tick, ergo we add one whole tick to the final duration. |
Ewout van Bekkum | 5ff8cc5 | 2021-09-07 15:46:36 -0700 | [diff] [blame] | 56 | const int lock_count = |
| 57 | OS_UseTimed(&native_handle(), static_cast<OS_TIME>(timeout.count() + 1)); |
Ewout van Bekkum | d5f83f9 | 2021-11-05 12:31:28 -0700 | [diff] [blame] | 58 | PW_DCHECK_UINT_LE(1, lock_count, "Recursive locking is not permitted"); |
Ewout van Bekkum | 99a6c20 | 2021-03-05 08:44:29 -0800 | [diff] [blame] | 59 | return lock_count == 1; |
| 60 | } |
| 61 | |
| 62 | } // namespace pw::sync |