1 #ifndef _UAPI_LINUX_MEMBARRIER_H 2 #define _UAPI_LINUX_MEMBARRIER_H 3 4 /* 5 * linux/membarrier.h 6 * 7 * membarrier system call API 8 * 9 * Copyright (c) 2010, 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> 10 * 11 * Permission is hereby granted, free of charge, to any person obtaining a copy 12 * of this software and associated documentation files (the "Software"), to deal 13 * in the Software without restriction, including without limitation the rights 14 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 15 * copies of the Software, and to permit persons to whom the Software is 16 * furnished to do so, subject to the following conditions: 17 * 18 * The above copyright notice and this permission notice shall be included in 19 * all copies or substantial portions of the Software. 20 * 21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 22 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 23 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 24 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 25 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 26 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 27 * SOFTWARE. 28 */ 29 30 /** 31 * enum membarrier_cmd - membarrier system call command 32 * @MEMBARRIER_CMD_QUERY: Query the set of supported commands. It returns 33 * a bitmask of valid commands. 34 * @MEMBARRIER_CMD_SHARED: Execute a memory barrier on all running threads. 35 * Upon return from system call, the caller thread 36 * is ensured that all running threads have passed 37 * through a state where all memory accesses to 38 * user-space addresses match program order between 39 * entry to and return from the system call 40 * (non-running threads are de facto in such a 41 * state). This covers threads from all processes 42 * running on the system. This command returns 0. 43 * @MEMBARRIER_CMD_PRIVATE_EXPEDITED: 44 * Execute a memory barrier on each running 45 * thread belonging to the same process as the current 46 * thread. Upon return from system call, the 47 * caller thread is ensured that all its running 48 * threads siblings have passed through a state 49 * where all memory accesses to user-space 50 * addresses match program order between entry 51 * to and return from the system call 52 * (non-running threads are de facto in such a 53 * state). This only covers threads from the 54 * same processes as the caller thread. This 55 * command returns 0 on success. The 56 * "expedited" commands complete faster than 57 * the non-expedited ones, they never block, 58 * but have the downside of causing extra 59 * overhead. A process needs to register its 60 * intent to use the private expedited command 61 * prior to using it, otherwise this command 62 * returns -EPERM. 63 * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED: 64 * Register the process intent to use 65 * MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always 66 * returns 0. 67 * 68 * Command to be passed to the membarrier system call. The commands need to 69 * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to 70 * the value 0. 71 */ 72 enum membarrier_cmd { 73 MEMBARRIER_CMD_QUERY = 0, 74 MEMBARRIER_CMD_SHARED = (1 << 0), 75 /* reserved for MEMBARRIER_CMD_SHARED_EXPEDITED (1 << 1) */ 76 /* reserved for MEMBARRIER_CMD_PRIVATE (1 << 2) */ 77 MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3), 78 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4), 79 }; 80 81 #endif /* _UAPI_LINUX_MEMBARRIER_H */ 82