scheduling_mode.h (2410B)
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 21 #include "absl/base/config.h" 22 23 namespace absl { 24 ABSL_NAMESPACE_BEGIN 25 namespace base_internal { 26 27 // Used to describe how a thread may be scheduled. Typically associated with 28 // the declaration of a resource supporting synchronized access. 29 // 30 // SCHEDULE_COOPERATIVE_AND_KERNEL: 31 // Specifies that when waiting, a cooperative thread (e.g. a Fiber) may 32 // reschedule (using base::scheduling semantics); allowing other cooperative 33 // threads to proceed. 34 // 35 // SCHEDULE_KERNEL_ONLY: (Also described as "non-cooperative") 36 // Specifies that no cooperative scheduling semantics may be used, even if the 37 // current thread is itself cooperatively scheduled. This means that 38 // cooperative threads will NOT allow other cooperative threads to execute in 39 // their place while waiting for a resource of this type. Host operating system 40 // semantics (e.g. a futex) may still be used. 41 // 42 // When optional, clients should strongly prefer SCHEDULE_COOPERATIVE_AND_KERNEL 43 // by default. SCHEDULE_KERNEL_ONLY should only be used for resources on which 44 // base::scheduling (e.g. the implementation of a Scheduler) may depend. 45 // 46 // NOTE: Cooperative resources may not be nested below non-cooperative ones. 47 // This means that it is invalid to to acquire a SCHEDULE_COOPERATIVE_AND_KERNEL 48 // resource if a SCHEDULE_KERNEL_ONLY resource is already held. 49 enum SchedulingMode { 50 SCHEDULE_KERNEL_ONLY = 0, // Allow scheduling only the host OS. 51 SCHEDULE_COOPERATIVE_AND_KERNEL, // Also allow cooperative scheduling. 52 }; 53 54 } // namespace base_internal 55 ABSL_NAMESPACE_END 56 } // namespace absl 57 58 #endif // ABSL_BASE_INTERNAL_SCHEDULING_MODE_H_