include/uapi/linux/membarrier.h

   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 */