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_GLOBAL: 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_GLOBAL_EXPEDITED: 44 * Execute a memory barrier on all running threads 45 * of all processes which previously registered 46 * with MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED. 47 * Upon return from system call, the caller thread 48 * is ensured that all running threads have passed 49 * through a state where all memory accesses to 50 * user-space addresses match program order between 51 * entry to and return from the system call 52 * (non-running threads are de facto in such a 53 * state). This only covers threads from processes 54 * which registered with 55 * MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED. 56 * This command returns 0. Given that 57 * registration is about the intent to receive 58 * the barriers, it is valid to invoke 59 * MEMBARRIER_CMD_GLOBAL_EXPEDITED from a 60 * non-registered process. 61 * @MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED: 62 * Register the process intent to receive 63 * MEMBARRIER_CMD_GLOBAL_EXPEDITED memory 64 * barriers. Always returns 0. 65 * @MEMBARRIER_CMD_PRIVATE_EXPEDITED: 66 * Execute a memory barrier on each running 67 * thread belonging to the same process as the current 68 * thread. Upon return from system call, the 69 * caller thread is ensured that all its running 70 * threads siblings have passed through a state 71 * where all memory accesses to user-space 72 * addresses match program order between entry 73 * to and return from the system call 74 * (non-running threads are de facto in such a 75 * state). This only covers threads from the 76 * same process as the caller thread. This 77 * command returns 0 on success. The 78 * "expedited" commands complete faster than 79 * the non-expedited ones, they never block, 80 * but have the downside of causing extra 81 * overhead. A process needs to register its 82 * intent to use the private expedited command 83 * prior to using it, otherwise this command 84 * returns -EPERM. 85 * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED: 86 * Register the process intent to use 87 * MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always 88 * returns 0. 89 * @MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE: 90 * In addition to provide memory ordering 91 * guarantees described in 92 * MEMBARRIER_CMD_PRIVATE_EXPEDITED, ensure 93 * the caller thread, upon return from system 94 * call, that all its running threads siblings 95 * have executed a core serializing 96 * instruction. (architectures are required to 97 * guarantee that non-running threads issue 98 * core serializing instructions before they 99 * resume user-space execution). This only 100 * covers threads from the same process as the 101 * caller thread. This command returns 0 on 102 * success. The "expedited" commands complete 103 * faster than the non-expedited ones, they 104 * never block, but have the downside of 105 * causing extra overhead. If this command is 106 * not implemented by an architecture, -EINVAL 107 * is returned. A process needs to register its 108 * intent to use the private expedited sync 109 * core command prior to using it, otherwise 110 * this command returns -EPERM. 111 * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE: 112 * Register the process intent to use 113 * MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE. 114 * If this command is not implemented by an 115 * architecture, -EINVAL is returned. 116 * Returns 0 on success. 117 * @MEMBARRIER_CMD_SHARED: 118 * Alias to MEMBARRIER_CMD_GLOBAL. Provided for 119 * header backward compatibility. 120 * 121 * Command to be passed to the membarrier system call. The commands need to 122 * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to 123 * the value 0. 124 */ 125 enum membarrier_cmd { 126 MEMBARRIER_CMD_QUERY = 0, 127 MEMBARRIER_CMD_GLOBAL = (1 << 0), 128 MEMBARRIER_CMD_GLOBAL_EXPEDITED = (1 << 1), 129 MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED = (1 << 2), 130 MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3), 131 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4), 132 MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 5), 133 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6), 134 135 /* Alias for header backward compatibility. */ 136 MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL, 137 }; 138 139 #endif /* _UAPI_LINUX_MEMBARRIER_H */ 140