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// Copyright 2017 The Abseil 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.

//

// Core interfaces and definitions used by by low-level interfaces such as

// SpinLock.

#ifndef ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_

#define ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_

#include "absl/base/config.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace base_internal {

// Used to describe how a thread may be scheduled.  Typically associated with

// the declaration of a resource supporting synchronized access.

//

// SCHEDULE_COOPERATIVE_AND_KERNEL:

// Specifies that when waiting, a cooperative thread (e.g. a Fiber) may

// reschedule (using base::scheduling semantics); allowing other cooperative

// threads to proceed.

//

// SCHEDULE_KERNEL_ONLY: (Also described as "non-cooperative")

// Specifies that no cooperative scheduling semantics may be used, even if the

// current thread is itself cooperatively scheduled.  This means that

// cooperative threads will NOT allow other cooperative threads to execute in

// their place while waiting for a resource of this type.  Host operating system

// semantics (e.g. a futex) may still be used.

//

// When optional, clients should strongly prefer SCHEDULE_COOPERATIVE_AND_KERNEL

// by default.  SCHEDULE_KERNEL_ONLY should only be used for resources on which

// base::scheduling (e.g. the implementation of a Scheduler) may depend.

//

// NOTE: Cooperative resources may not be nested below non-cooperative ones.

// This means that it is invalid to to acquire a SCHEDULE_COOPERATIVE_AND_KERNEL

// resource if a SCHEDULE_KERNEL_ONLY resource is already held.

enum SchedulingMode {

  SCHEDULE_KERNEL_ONLY = 0,         // Allow scheduling only the host OS.

  SCHEDULE_COOPERATIVE_AND_KERNEL,  // Also allow cooperative scheduling.

};

}  // namespace base_internal

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_