pw_sync_embos/interrupt_spin_lock.cc

// 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/interrupt_spin_lock.h"

#include "RTOS.h"
#include "pw_assert/check.h"

namespace pw::sync {

void InterruptSpinLock::lock() {
  OS_IncDI();
  // We can't deadlock here so crash instead.
  PW_CHECK(!native_type_.locked.load(std::memory_order_relaxed),
           "Recursive InterruptSpinLock::lock() detected");
  native_type_.locked.store(true, std::memory_order_relaxed);
}

bool InterruptSpinLock::try_lock() {
  OS_IncDI();
  if (native_type_.locked.load(std::memory_order_relaxed)) {
    OS_DecRI();  // Already locked, restore interrupts and bail out.
    return false;
  }
  native_type_.locked.store(true, std::memory_order_relaxed);
  return true;
}

void InterruptSpinLock::unlock() {
  native_type_.locked.store(false, std::memory_order_relaxed);
  OS_DecRI();
}

}  // namespace pw::sync