1// Copyright 2017 The Abseil Authors.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15// Core interfaces and definitions used by by low-level interfaces such as
16// SpinLock.
17
18#ifndef ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_
19#define ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_
20
21namespace absl {
22namespace base_internal {
23
24// Used to describe how a thread may be scheduled. Typically associated with
25// the declaration of a resource supporting synchronized access.
26//
27// SCHEDULE_COOPERATIVE_AND_KERNEL:
28// Specifies that when waiting, a cooperative thread (e.g. a Fiber) may
29// reschedule (using base::scheduling semantics); allowing other cooperative
30// threads to proceed.
31//
32// SCHEDULE_KERNEL_ONLY: (Also described as "non-cooperative")
33// Specifies that no cooperative scheduling semantics may be used, even if the
34// current thread is itself cooperatively scheduled. This means that
35// cooperative threads will NOT allow other cooperative threads to execute in
36// their place while waiting for a resource of this type. Host operating system
37// semantics (e.g. a futex) may still be used.
38//
39// When optional, clients should strongly prefer SCHEDULE_COOPERATIVE_AND_KERNEL
40// by default. SCHEDULE_KERNEL_ONLY should only be used for resources on which
41// base::scheduling (e.g. the implementation of a Scheduler) may depend.
42//
43// NOTE: Cooperative resources may not be nested below non-cooperative ones.
44// This means that it is invalid to to acquire a SCHEDULE_COOPERATIVE_AND_KERNEL
45// resource if a SCHEDULE_KERNEL_ONLY resource is already held.
46enum SchedulingMode {
47 SCHEDULE_KERNEL_ONLY = 0, // Allow scheduling only the host OS.
48 SCHEDULE_COOPERATIVE_AND_KERNEL, // Also allow cooperative scheduling.
49};
50
51} // namespace base_internal
52} // namespace absl
53
54#endif // ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_
55