108 lines
4.1 KiB
C++
108 lines
4.1 KiB
C++
// Copyright 2021 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_sync/timed_thread_notification.h"
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#include <algorithm>
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#include "FreeRTOS.h"
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#include "pw_assert/check.h"
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#include "pw_chrono/system_clock.h"
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#include "pw_chrono_freertos/system_clock_constants.h"
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#include "pw_interrupt/context.h"
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#include "pw_sync_freertos/config.h"
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#include "task.h"
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using pw::chrono::SystemClock;
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namespace pw::sync {
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namespace {
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BaseType_t WaitForNotification(TickType_t xTicksToWait) {
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#ifdef configTASK_NOTIFICATION_ARRAY_ENTRIES
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return xTaskNotifyWaitIndexed(
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pw::sync::freertos::config::kThreadNotificationIndex,
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0, // Clear no bits on entry.
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0, // Clear no bits on exit.
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nullptr, // Don't care about the notification value.
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xTicksToWait);
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#else // !configTASK_NOTIFICATION_ARRAY_ENTRIES
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return xTaskNotifyWait(0, // Clear no bits on entry.
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0, // Clear no bits on exit.
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nullptr, // Don't care about the notification value.
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xTicksToWait);
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#endif // configTASK_NOTIFICATION_ARRAY_ENTRIES
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}
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} // namespace
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bool TimedThreadNotification::try_acquire_until(
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const SystemClock::time_point deadline) {
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// Enforce the pw::sync::TImedThreadNotification IRQ contract.
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PW_DCHECK(!interrupt::InInterruptContext());
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// Enforce that only a single thread can block at a time.
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PW_DCHECK(native_handle().blocked_thread == nullptr);
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// Ensure that no one forgot to clean up nor corrupted the task notification
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// state in the TCB.
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PW_DCHECK(xTaskNotifyStateClear(nullptr) == pdFALSE);
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{
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std::lock_guard lock(native_handle().shared_spin_lock);
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const bool notified = native_handle().notified;
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// Don't block if we've already reached the specified deadline time.
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if (notified || (SystemClock::now() >= deadline)) {
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native_handle().notified = false;
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return notified;
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}
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// Not notified yet, set the task handle for a one-time notification.
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native_handle().blocked_thread = xTaskGetCurrentTaskHandle();
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}
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// xTaskNotifyWait may spuriously return pdFALSE due to vTaskSuspend &
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// vTaskResume. Ergo, loop until we have been notified or the specified
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// deadline time has been reached (whichever comes first).
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for (SystemClock::time_point now = SystemClock::now(); now < deadline;
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now = SystemClock::now()) {
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// Note that this must be greater than zero, due to the condition above.
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const SystemClock::duration timeout =
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std::min(deadline - now, pw::chrono::freertos::kMaxTimeout);
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if (WaitForNotification(static_cast<TickType_t>(timeout.count())) ==
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pdTRUE) {
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break; // We were notified!
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}
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}
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std::lock_guard lock(native_handle().shared_spin_lock);
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// We need to clear the thread notification state in case we were
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// notified after timing out but before entering this critical section.
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#ifdef configTASK_NOTIFICATION_ARRAY_ENTRIES
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xTaskNotifyStateClearIndexed(
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nullptr, pw::sync::freertos::config::kThreadNotificationIndex);
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#else // !configTASK_NOTIFICATION_ARRAY_ENTRIES
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xTaskNotifyStateClear(nullptr);
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#endif // configTASK_NOTIFICATION_ARRAY_ENTRIES
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// Instead of determining whether we were notified above while blocking in
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// the loop above, we instead read it in this subsequent critical section in
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// order to also include notifications which arrived after we timed out but
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// before we entered this critical section.
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const bool notified = native_handle().notified;
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native_handle().notified = false;
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native_handle().blocked_thread = nullptr;
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return notified;
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}
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} // namespace pw::sync
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