// bthread - A M:N threading library to make applications more concurrent. // Copyright (c) 2014 Baidu, Inc. // // 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 // // http://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. // Author: Ge,Jun (gejun@baidu.com) // Date: Fri Dec 5 13:40:57 CST 2014 #ifndef BTHREAD_PROCESSOR_H #define BTHREAD_PROCESSOR_H // Pause instruction to prevent excess processor bus usage, only works in GCC # ifndef cpu_relax # define cpu_relax() asm volatile("pause\n": : :"memory") # endif // Compile read-write barrier # ifndef barrier # define barrier() asm volatile("": : :"memory") # endif # define BT_LOOP_WHEN(expr, num_spins) \ do { \ /*sched_yield may change errno*/ \ const int saved_errno = errno; \ for (int cnt = 0, saved_nspin = (num_spins); (expr); ++cnt) { \ if (cnt < saved_nspin) { \ cpu_relax(); \ } else { \ sched_yield(); \ } \ } \ errno = saved_errno; \ } while (0) #endif // BTHREAD_PROCESSOR_H