hurd/hurd/port.h

   1 /* Lightweight user references for ports.
   2    Copyright (C) 1993-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _HURD_PORT_H
  20
  21 #define _HURD_PORT_H    1
  22 #include <features.h>
  23
  24 #include <mach.h>
  25 #include <hurd/userlink.h>
  26 #include <spin-lock.h>
  27
  28
  29 /* Structure describing a cell containing a port.  With the lock held, a
  30    user extracts PORT, and attaches his own link (in local storage) to the
  31    USERS chain.  PORT can then safely be used.  When PORT is no longer
  32    needed, with the lock held, the user removes his link from the chain.
  33    If his link is the last, and PORT has changed since he fetched it, the
  34    user deallocates the port he used.  See <hurd/userlink.h>.  */
  35
  36 struct hurd_port
  37   {
  38     spin_lock_t lock;           /* Locks rest.  */
  39     struct hurd_userlink *users; /* Chain of users; see below.  */
  40     mach_port_t port;           /* Port. */
  41   };
  42
  43
  44 /* Evaluate EXPR with the variable `port' bound to the port in PORTCELL.  */
  45
  46 #define HURD_PORT_USE(portcell, expr)                                         \
  47   ({ struct hurd_port *const __p = (portcell);                                \
  48      struct hurd_userlink __link;                                             \
  49      const mach_port_t port = _hurd_port_get (__p, &__link);                  \
  50      __typeof(expr) __result = (expr);                                        \
  51      _hurd_port_free (__p, &__link, port);                                    \
  52      __result; })
  53
  54
  55 #ifndef _HURD_PORT_H_EXTERN_INLINE
  56 #define _HURD_PORT_H_EXTERN_INLINE __extern_inline
  57 #endif
  58
  59
  60 /* Initialize *PORT to INIT.  */
  61
  62 extern void _hurd_port_init (struct hurd_port *port, mach_port_t init);
  63
  64 #if defined __USE_EXTERN_INLINES && defined _LIBC
  65 # if IS_IN (libc)
  66 _HURD_PORT_H_EXTERN_INLINE void
  67 _hurd_port_init (struct hurd_port *port, mach_port_t init)
  68 {
  69   __spin_lock_init (&port->lock);
  70   port->users = NULL;
  71   port->port = init;
  72 }
  73 # endif
  74 #endif
  75
  76
  77 /* Cleanup function for non-local exits.  */
  78 extern void _hurd_port_cleanup (void *, jmp_buf, int);
  79
  80 /* Get a reference to *PORT, which is locked.
  81    Pass return value and LINK to _hurd_port_free when done.  */
  82
  83 extern mach_port_t
  84 _hurd_port_locked_get (struct hurd_port *port,
  85                        struct hurd_userlink *link);
  86
  87 #if defined __USE_EXTERN_INLINES && defined _LIBC
  88 # if IS_IN (libc)
  89 _HURD_PORT_H_EXTERN_INLINE mach_port_t
  90 _hurd_port_locked_get (struct hurd_port *port,
  91                        struct hurd_userlink *link)
  92 {
  93   mach_port_t result;
  94   result = port->port;
  95   if (result != MACH_PORT_NULL)
  96     {
  97       link->cleanup = &_hurd_port_cleanup;
  98       link->cleanup_data = (void *) result;
  99       _hurd_userlink_link (&port->users, link);
 100     }
 101   __spin_unlock (&port->lock);
 102   return result;
 103 }
 104 # endif
 105 #endif
 106
 107 /* Same, but locks PORT first.  */
 108
 109 extern mach_port_t
 110 _hurd_port_get (struct hurd_port *port,
 111                 struct hurd_userlink *link);
 112
 113 #if defined __USE_EXTERN_INLINES && defined _LIBC
 114 # if IS_IN (libc)
 115 _HURD_PORT_H_EXTERN_INLINE mach_port_t
 116 _hurd_port_get (struct hurd_port *port,
 117                 struct hurd_userlink *link)
 118 {
 119   mach_port_t result;
 120   HURD_CRITICAL_BEGIN;
 121   __spin_lock (&port->lock);
 122   result = _hurd_port_locked_get (port, link);
 123   HURD_CRITICAL_END;
 124   return result;
 125 }
 126 # endif
 127 #endif
 128
 129
 130 /* Free a reference gotten with `USED_PORT = _hurd_port_get (PORT, LINK);' */
 131
 132 extern void
 133 _hurd_port_free (struct hurd_port *port,
 134                  struct hurd_userlink *link,
 135                  mach_port_t used_port);
 136
 137 #if defined __USE_EXTERN_INLINES && defined _LIBC
 138 # if IS_IN (libc)
 139 _HURD_PORT_H_EXTERN_INLINE void
 140 _hurd_port_free (struct hurd_port *port,
 141                  struct hurd_userlink *link,
 142                  mach_port_t used_port)
 143 {
 144   int dealloc;
 145   if (used_port == MACH_PORT_NULL)
 146     /* When we fetch an empty port cell with _hurd_port_get,
 147        it does not link us on the users chain, since there is
 148        no shared resource.  */
 149     return;
 150   HURD_CRITICAL_BEGIN;
 151   __spin_lock (&port->lock);
 152   dealloc = _hurd_userlink_unlink (link);
 153   __spin_unlock (&port->lock);
 154   HURD_CRITICAL_END;
 155   if (dealloc)
 156     __mach_port_deallocate (__mach_task_self (), used_port);
 157 }
 158 # endif
 159 #endif
 160
 161
 162 /* Set *PORT's port to NEWPORT.  NEWPORT's reference is consumed by PORT->port.
 163    PORT->lock is locked.  */
 164
 165 extern void _hurd_port_locked_set (struct hurd_port *port, mach_port_t newport);
 166
 167 #if defined __USE_EXTERN_INLINES && defined _LIBC
 168 # if IS_IN (libc)
 169 _HURD_PORT_H_EXTERN_INLINE void
 170 _hurd_port_locked_set (struct hurd_port *port, mach_port_t newport)
 171 {
 172   mach_port_t old;
 173   old = _hurd_userlink_clear (&port->users) ? port->port : MACH_PORT_NULL;
 174   port->port = newport;
 175   __spin_unlock (&port->lock);
 176   if (old != MACH_PORT_NULL)
 177     __mach_port_deallocate (__mach_task_self (), old);
 178 }
 179 # endif
 180 #endif
 181
 182 /* Same, but locks PORT first.  */
 183
 184 extern void _hurd_port_set (struct hurd_port *port, mach_port_t newport);
 185
 186 #if defined __USE_EXTERN_INLINES && defined _LIBC
 187 # if IS_IN (libc)
 188 _HURD_PORT_H_EXTERN_INLINE void
 189 _hurd_port_set (struct hurd_port *port, mach_port_t newport)
 190 {
 191   HURD_CRITICAL_BEGIN;
 192   __spin_lock (&port->lock);
 193   _hurd_port_locked_set (port, newport);
 194   HURD_CRITICAL_END;
 195 }
 196 # endif
 197 #endif
 198
 199
 200 #endif  /* hurd/port.h */