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// 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/timed_mutex.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 TimedMutex::try_lock_for(SystemClock::duration for_at_least) {
// Enforce the pw::sync::TimedMutex IRQ contract.
// Use non-blocking try_lock for negative or zero length durations.
if (for_at_least <= SystemClock::duration::zero()) {
return try_lock();
// 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_mutex_get(
&native_type_, static_cast<ULONG>(kMaxTimeoutMinusOne.count()));
if (result != TX_NOT_AVAILABLE) {
return true;
for_at_least -= kMaxTimeoutMinusOne;
const UINT result =
tx_mutex_get(&native_type_, static_cast<ULONG>(for_at_least.count() + 1));
if (result == TX_NOT_AVAILABLE) {
return false;
return true;
} // namespace pw::sync