blob: 298da13e825094827d01401f005cdf523ec4d8db [file] [log] [blame]
// 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
// 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 "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"
using pw::chrono::SystemClock;
namespace pw::sync {
bool CountingSemaphore::try_acquire_for(SystemClock::duration for_at_least) {
// Enforce the pw::sync::CountingSemaphore IRQ contract.
// Use non-blocking try_acquire for negative and zero length durations.
if (for_at_least <= 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::threadx::kMaxTimeout - SystemClock::duration(1);
while (for_at_least > kMaxTimeoutMinusOne) {
const UINT result = tx_semaphore_get(
&native_type_, static_cast<ULONG>(kMaxTimeoutMinusOne.count()));
if (result != TX_NO_INSTANCE) {
// If we didn't time out (TX_NO_INSTANCE), then we should have succeeded.
return true;
for_at_least -= kMaxTimeoutMinusOne;
const UINT result = tx_semaphore_get(
&native_type_, static_cast<ULONG>(for_at_least.count() + 1));
if (result == TX_NO_INSTANCE) {
return false; // We timed out, there's still no token.
return true;
} // namespace pw::sync