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_PRIVATE_EXPEDITED_RSEQ:
118  *                          Ensure the caller thread, upon return from
119  *                          system call, that all its running thread
120  *                          siblings have any currently running rseq
121  *                          critical sections restarted if @flags
122  *                          parameter is 0; if @flags parameter is
123  *                          MEMBARRIER_CMD_FLAG_CPU,
124  *                          then this operation is performed only
125  *                          on CPU indicated by @cpu_id. If this command is
126  *                          not implemented by an architecture, -EINVAL
127  *                          is returned. A process needs to register its
128  *                          intent to use the private expedited rseq
129  *                          command prior to using it, otherwise
130  *                          this command returns -EPERM.
131  * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ:
132  *                          Register the process intent to use
133  *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ.
134  *                          If this command is not implemented by an
135  *                          architecture, -EINVAL is returned.
136  *                          Returns 0 on success.
137  * @MEMBARRIER_CMD_SHARED:
138  *                          Alias to MEMBARRIER_CMD_GLOBAL. Provided for
139  *                          header backward compatibility.
140  * @MEMBARRIER_CMD_GET_REGISTRATIONS:
141  *                          Returns a bitmask of previously issued
142  *                          registration commands.
143  *
144  * Command to be passed to the membarrier system call. The commands need to
145  * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to
146  * the value 0.
147  */
148 enum membarrier_cmd {
149 	MEMBARRIER_CMD_QUERY					= 0,
150 	MEMBARRIER_CMD_GLOBAL					= (1 << 0),
151 	MEMBARRIER_CMD_GLOBAL_EXPEDITED				= (1 << 1),
152 	MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED		= (1 << 2),
153 	MEMBARRIER_CMD_PRIVATE_EXPEDITED			= (1 << 3),
154 	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED		= (1 << 4),
155 	MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE		= (1 << 5),
156 	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE	= (1 << 6),
157 	MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ			= (1 << 7),
158 	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ		= (1 << 8),
159 	MEMBARRIER_CMD_GET_REGISTRATIONS			= (1 << 9),
160 
161 	/* Alias for header backward compatibility. */
162 	MEMBARRIER_CMD_SHARED			= MEMBARRIER_CMD_GLOBAL,
163 };
164 
165 enum membarrier_cmd_flag {
166 	MEMBARRIER_CMD_FLAG_CPU		= (1 << 0),
167 };
168 
169 #endif /* _UAPI_LINUX_MEMBARRIER_H */
170