126 lines
4.8 KiB
C++
126 lines
4.8 KiB
C++
// Copyright 2021 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 "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 "pw_sync_freertos/config.h"
|
|
#include "task.h"
|
|
|
|
using pw::chrono::SystemClock;
|
|
|
|
namespace pw::sync {
|
|
namespace {
|
|
|
|
BaseType_t WaitForNotification(TickType_t xTicksToWait) {
|
|
#ifdef configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
return xTaskNotifyWaitIndexed(
|
|
pw::sync::freertos::config::kThreadNotificationIndex,
|
|
0, // Clear no bits on entry.
|
|
0, // Clear no bits on exit.
|
|
nullptr, // Don't care about the notification value.
|
|
xTicksToWait);
|
|
#else // !configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
return xTaskNotifyWait(0, // Clear no bits on entry.
|
|
0, // Clear no bits on exit.
|
|
nullptr, // Don't care about the notification value.
|
|
xTicksToWait);
|
|
#endif // configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
}
|
|
|
|
} // namespace
|
|
|
|
bool TimedThreadNotification::try_acquire_for(SystemClock::duration timeout) {
|
|
// Enforce the pw::sync::TImedThreadNotification IRQ contract.
|
|
PW_DCHECK(!interrupt::InInterruptContext());
|
|
|
|
// Enforce that only a single thread can block at a time.
|
|
PW_DCHECK(native_handle().blocked_thread == nullptr);
|
|
|
|
// Ensure that no one forgot to clean up nor corrupted the task notification
|
|
// state in the TCB.
|
|
PW_DCHECK(xTaskNotifyStateClear(nullptr) == pdFALSE);
|
|
|
|
taskENTER_CRITICAL();
|
|
{
|
|
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;
|
|
taskEXIT_CRITICAL();
|
|
return notified;
|
|
}
|
|
// Not notified yet, set the task handle for a one-time notification.
|
|
native_handle().blocked_thread = xTaskGetCurrentTaskHandle();
|
|
}
|
|
taskEXIT_CRITICAL();
|
|
|
|
const bool notified = [&]() {
|
|
// 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);
|
|
// In case the timeout is too long for us to express through the native
|
|
// FreeRTOS API, we repeatedly wait with shorter durations.
|
|
while (timeout > kMaxTimeoutMinusOne) {
|
|
if (WaitForNotification(
|
|
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 WaitForNotification(static_cast<TickType_t>(timeout.count() + 1)) ==
|
|
pdTRUE;
|
|
}();
|
|
|
|
taskENTER_CRITICAL();
|
|
if (notified) {
|
|
// Note that this may hide another notification, however this is considered
|
|
// a form of notification saturation just like as if this happened before
|
|
// acquire() was invoked.
|
|
native_handle().notified = false;
|
|
// The task handle and notification state were 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 task handle if we weren't notified and
|
|
// the notification state in case we were notified to ensure we can block
|
|
// in the future.
|
|
native_handle().blocked_thread = nullptr;
|
|
#ifdef configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
xTaskNotifyStateClearIndexed(
|
|
nullptr, pw::sync::freertos::config::kThreadNotificationIndex);
|
|
#else // !configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
xTaskNotifyStateClear(nullptr);
|
|
#endif // configTASK_NOTIFICATION_ARRAY_ENTRIES
|
|
}
|
|
taskEXIT_CRITICAL();
|
|
return notified;
|
|
}
|
|
|
|
} // namespace pw::sync
|