blob: 639042666241d907e9cd3aefa796e2b39b54627e [file] [log] [blame]
// 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
// 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/counting_semaphore.h"
#include <algorithm>
#include "RTOS.h"
#include "pw_assert/check.h"
#include "pw_chrono/system_clock.h"
#include "pw_chrono_embos/system_clock_constants.h"
#include "pw_interrupt/context.h"
using pw::chrono::SystemClock;
namespace pw::sync {
void CountingSemaphore::release(ptrdiff_t update) {
for (; update > 0; --update) {
// There is no API to atomically detect overflow, however debug builds of
// embOS call OS_Error() internally when overflow is detected for the native
// token representation. Rather than enter a critical section both due to
// cost and potential direct use of the native handle, a lazy check is used
// for debug builds which may not trigger on the initial overflow.
"Overflowed counting semaphore.");
bool CountingSemaphore::try_acquire_for(SystemClock::duration timeout) {
// Use non-blocking try_acquire for negative and zero length durations.
if (timeout <= SystemClock::duration::zero()) {
return try_acquire();
// 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::embos::kMaxTimeout - SystemClock::duration(1);
while (timeout > kMaxTimeoutMinusOne) {
if (OS_WaitCSemaTimed(&native_type_,
static_cast<OS_TIME>(kMaxTimeoutMinusOne.count()))) {
return true;
timeout -= kMaxTimeoutMinusOne;
return OS_WaitCSemaTimed(&native_type_,
static_cast<OS_TIME>(timeout.count() + 1));
} // namespace pw::sync