| // 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/timed_thread_notification.h" |
| |
| #include <mutex> |
| |
| #include "pw_assert/check.h" |
| #include "pw_chrono/system_clock.h" |
| #include "pw_chrono_threadx/system_clock_constants.h" |
| #include "pw_interrupt/context.h" |
| #include "tx_api.h" |
| |
| namespace pw::sync { |
| namespace { |
| |
| using pw::chrono::SystemClock; |
| |
| } // namespace |
| |
| bool TimedThreadNotification::try_acquire_for(SystemClock::duration timeout) { |
| PW_DCHECK(!interrupt::InInterruptContext()); |
| PW_DCHECK(native_handle().blocked_thread == nullptr); |
| { |
| std::lock_guard lock(backend::thread_notification_isl); |
| const bool notified = native_handle().notified; |
| // Don't block for negative or zero length durations. |
| if (notified || timeout <= SystemClock::duration::zero()) { |
| native_handle().notified = false; |
| return notified; |
| } |
| // Not notified yet, register the thread for a one-time notification. |
| native_handle().blocked_thread = tx_thread_identify(); |
| } |
| |
| const bool notified = [&]() { |
| // 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::threadx::kMaxTimeout - SystemClock::duration(1); |
| // In case the timeout is too long for us to express through the native |
| // ThreadX API, we repeatedly wait with shorter durations. |
| while (timeout > kMaxTimeoutMinusOne) { |
| const UINT result = |
| tx_thread_sleep(static_cast<ULONG>(kMaxTimeoutMinusOne.count())); |
| if (result != TX_SUCCESS) { |
| PW_CHECK_UINT_EQ(TX_WAIT_ABORTED, result); |
| return true; |
| } |
| timeout -= kMaxTimeoutMinusOne; |
| } |
| |
| const UINT result = |
| tx_thread_sleep(static_cast<ULONG>(timeout.count() + 1)); |
| if (result == TX_SUCCESS) { |
| return false; |
| } |
| PW_CHECK_UINT_EQ(TX_WAIT_ABORTED, result); |
| return true; |
| }(); |
| |
| { |
| std::lock_guard lock(backend::thread_notification_isl); |
| if (notified) { |
| // Note that this may hide another notification, however this is |
| // considered form of notification saturation just like as if this |
| // happened before acquire() was invoked. |
| native_handle().notified = false; |
| // The thread pointer was cleared by the notifier. |
| } else { |
| // Note that we do NOT want to clear the notified value so the next call |
| // can detect the notification which came after we timed out but before |
| // this critical section. |
| // |
| // However, we do need to clear the thread pointer if we weren't notified. |
| native_handle().blocked_thread = nullptr; |
| } |
| } |
| return notified; |
| } |
| |
| } // namespace pw::sync |