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 */