gcc/config/vxlib.c

   1 /* Copyright (C) 2002 Free Software Foundation, Inc.
   2    Contributed by Zack Weinberg <zack@codesourcery.com>
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  19 02111-1307, USA.  */
  20
  21 /* Threads compatibility routines for libgcc2 for VxWorks.
  22    These are out-of-line routines called from gthr-vxworks.h.  */
  23
  24 /* As a special exception, if you link this library with other files,
  25    some of which are compiled with GCC, to produce an executable,
  26    this library does not by itself cause the resulting executable
  27    to be covered by the GNU General Public License.
  28    This exception does not however invalidate any other reasons why
  29    the executable file might be covered by the GNU General Public License.  */
  30
  31 #include "tconfig.h"
  32 #include "tsystem.h"
  33 #include "gthr.h"
  34
  35 #include <vxWorks.h>
  36 #include <vxLib.h>
  37 #include <taskLib.h>
  38 #include <taskHookLib.h>
  39
  40 /* Init-once operation.
  41
  42    This would be a clone of the implementation from gthr-solaris.h,
  43    except that we have a bootstrap problem - the whole point of this
  44    exercise is to prevent double initialization, but if two threads
  45    are racing with each other, once->mutex is liable to be initialized
  46    by both.  Then each thread will lock its own mutex, and proceed to
  47    call the initialization routine.
  48
  49    So instead we use a bare atomic primitive (vxTas()) to handle
  50    mutual exclusion.  Threads losing the race then busy-wait, calling
  51    taskDelay() to yield the processor, until the initialization is
  52    completed.  Inefficient, but reliable.  */
  53
  54 int
  55 __gthread_once (__gthread_once_t *guard, void (*func)(void))
  56 {
  57   if (guard->done)
  58     return 0;
  59
  60   while (!vxTas ((void *)&guard->busy))
  61     taskDelay (1);
  62
  63   /* Only one thread at a time gets here.  Check ->done again, then
  64      go ahead and call func() if no one has done it yet.  */
  65   if (!guard->done)
  66     {
  67       func ();
  68       guard->done = 1;
  69     }
  70
  71   guard->busy = 0;
  72   return 0;
  73 }
  74
  75 /* Thread-specific data.
  76
  77    We reserve a field in the TCB to point to a dynamically allocated
  78    array which is used to store TSD values.  A TSD key is simply an
  79    offset in this array.  The exact location of the TCB field is not
  80    known to this code nor to vxlib.c -- all access to it indirects
  81    through the routines __gthread_get_tsd_data and
  82    __gthread_set_tsd_data, which are provided by the VxWorks kernel.
  83
  84    There is also a global array which records which keys are valid and
  85    which have destructors.
  86
  87    A task delete hook is installed to execute key destructors.  The
  88    routines __gthread_enter_tsd_dtor_context and
  89    __gthread_leave_tsd_dtor_context, which are also provided by the
  90    kernel, ensure that it is safe to call free() on memory allocated
  91    by the task being deleted.  (This is a no-op on VxWorks 5, but
  92    a major undertaking on AE.)
  93
  94    Since this interface is used to allocate only a small number of
  95    keys, the table size is small and static, which simplifies the
  96    code quite a bit.  Revisit this if and when it becomes necessary.  */
  97
  98 #define MAX_KEYS 4
  99
 100 /* This is the structure pointed to by the pointer returned
 101    by __gthread_get_tsd_data.  */
 102 struct tsd_data
 103 {
 104   void *values[MAX_KEYS];
 105   unsigned int generation[MAX_KEYS];
 106 };
 107
 108
 109 /* kernel provided routines */
 110 extern void *__gthread_get_tsd_data (WIND_TCB *tcb);
 111 extern void __gthread_set_tsd_data (WIND_TCB *tcb, void *data);
 112
 113 extern void __gthread_enter_tsd_dtor_context (WIND_TCB *tcb);
 114 extern void __gthread_leave_tsd_dtor_context (WIND_TCB *tcb);
 115
 116 typedef void (*fet_callback_t) (WIND_TCB *, unsigned int);
 117 extern void __gthread_for_all_tasks (fet_callback_t fun, unsigned int number);
 118
 119 /* This is a global structure which records all of the active keys.
 120
 121    A key is potentially valid (i.e. has been handed out by
 122    __gthread_key_create) iff its generation count in this structure is
 123    even.  In that case, the matching entry in the dtors array is a
 124    routine to be called when a thread terminates with a valid,
 125    non-NULL specific value for that key.
 126
 127    A key is actually valid in a thread T iff the generation count
 128    stored in this structure is equal to the generation count stored in
 129    T's specific-value structure.  */
 130
 131 typedef void (*tsd_dtor) (void *);
 132
 133 struct tsd_keys
 134 {
 135   tsd_dtor dtor[MAX_KEYS];
 136   unsigned int generation[MAX_KEYS];
 137 };
 138
 139 #define KEY_VALID_P(key) !(tsd_keys.generation[key] & 1)
 140
 141 /* Note: if MAX_KEYS is increased, this initializer must be updated
 142    to match.  All the generation counts begin at 1, which means no
 143    key is valid.  */
 144 static struct tsd_keys tsd_keys =
 145 {
 146   { 0, 0, 0, 0 },
 147   { 1, 1, 1, 1 }
 148 };
 149
 150 /* This lock protects the tsd_keys structure.  */
 151 static __gthread_mutex_t tsd_lock;
 152
 153 static __gthread_once_t tsd_init_guard = __GTHREAD_ONCE_INIT;
 154
 155 /* Internal routines.  */
 156
 157 /* The task TCB has just been deleted.  Call the destructor
 158    function for each TSD key that has both a destructor and
 159    a non-NULL specific value in this thread.
 160
 161    This routine does not need to take tsd_lock; the generation
 162    count protects us from calling a stale destructor.  It does
 163    need to read tsd_keys.dtor[key] atomically.  */
 164
 165 static void
 166 tsd_delete_hook (WIND_TCB *tcb)
 167 {
 168   struct tsd_data *data = __gthread_get_tsd_data (tcb);
 169   __gthread_key_t key;
 170
 171   if (data)
 172     {
 173       __gthread_enter_tsd_dtor_context (tcb);
 174       for (key = 0; key < MAX_KEYS; key++)
 175         {
 176           if (data->generation[key] == tsd_keys.generation[key])
 177             {
 178               tsd_dtor dtor = tsd_keys.dtor[key];
 179
 180               if (dtor)
 181                 dtor (data->values[key]);
 182             }
 183         }
 184       free (data);
 185       __gthread_set_tsd_data (tcb, 0);
 186       __gthread_leave_tsd_dtor_context (tcb);
 187     }
 188 }
 189
 190 /* Initialize global data used by the TSD system.  */
 191 static void
 192 tsd_init (void)
 193 {
 194   taskDeleteHookAdd ((FUNCPTR)tsd_delete_hook);
 195   __GTHREAD_MUTEX_INIT_FUNCTION (&tsd_lock);
 196 }
 197
 198 /* External interface */
 199
 200 /* Store in KEYP a value which can be passed to __gthread_setspecific/
 201    __gthread_getspecific to store and retrieve a value which is
 202    specific to each calling thread.  If DTOR is not NULL, it will be
 203    called when a thread terminates with a non-NULL specific value for
 204    this key, with the value as its sole argument.  */
 205
 206 int
 207 __gthread_key_create (__gthread_key_t *keyp, tsd_dtor dtor)
 208 {
 209   __gthread_key_t key;
 210
 211   __gthread_once (&tsd_init_guard, tsd_init);
 212
 213   if (__gthread_mutex_lock (&tsd_lock) == ERROR)
 214     return errno;
 215
 216   for (key = 0; key < MAX_KEYS; key++)
 217     if (!KEY_VALID_P (key))
 218       goto found_slot;
 219
 220   /* no room */
 221   __gthread_mutex_unlock (&tsd_lock);
 222   return EAGAIN;
 223
 224  found_slot:
 225   tsd_keys.generation[key]++;  /* making it even */
 226   tsd_keys.dtor[key] = dtor;
 227   *keyp = key;
 228   __gthread_mutex_unlock (&tsd_lock);
 229   return 0;
 230 }
 231
 232 /* Invalidate KEY; it can no longer be used as an argument to
 233    setspecific/getspecific.  Note that this does NOT call destructor
 234    functions for any live values for this key.  */
 235 int
 236 __gthread_key_delete (__gthread_key_t key)
 237 {
 238   if (key >= MAX_KEYS)
 239     return EINVAL;
 240
 241   __gthread_once (&tsd_init_guard, tsd_init);
 242
 243   if (__gthread_mutex_lock (&tsd_lock) == ERROR)
 244     return errno;
 245
 246   if (!KEY_VALID_P (key))
 247     {
 248       __gthread_mutex_unlock (&tsd_lock);
 249       return EINVAL;
 250     }
 251
 252   tsd_keys.generation[key]++;  /* making it odd */
 253   tsd_keys.dtor[key] = 0;
 254
 255   __gthread_mutex_unlock (&tsd_lock);
 256   return 0;
 257 }
 258
 259 /* Retrieve the thread-specific value for KEY.  If it has never been
 260    set in this thread, or KEY is invalid, returns NULL.
 261
 262    It does not matter if this function races with key_create or
 263    key_delete; the worst that can happen is you get a value other than
 264    the one that a serialized implementation would have provided.  */
 265
 266 void *
 267 __gthread_getspecific (__gthread_key_t key)
 268 {
 269   struct tsd_data *data;
 270
 271   if (key >= MAX_KEYS)
 272     return 0;
 273
 274   data = __gthread_get_tsd_data (taskTcb (taskIdSelf ()));
 275
 276   if (!data)
 277     return 0;
 278
 279   if (data->generation[key] != tsd_keys.generation[key])
 280     return 0;
 281
 282   return data->values[key];
 283 }
 284
 285 /* Set the thread-specific value for KEY.  If KEY is invalid, or
 286    memory allocation fails, returns -1, otherwise 0.
 287
 288    The generation count protects this function against races with
 289    key_create/key_delete; the worst thing that can happen is that a
 290    value is successfully stored into a dead generation (and then
 291    immediately becomes invalid).  However, we do have to make sure
 292    to read tsd_keys.generation[key] atomically.  */
 293
 294 int
 295 __gthread_setspecific (__gthread_key_t key, void *value)
 296 {
 297   struct tsd_data *data;
 298   WIND_TCB *tcb;
 299   unsigned int generation;
 300
 301   if (key >= MAX_KEYS)
 302     return EINVAL;
 303
 304   tcb = taskTcb (taskIdSelf ());
 305   data = __gthread_get_tsd_data (tcb);
 306   if (!data)
 307     {
 308       data = malloc (sizeof (struct tsd_data));
 309       if (!data)
 310         return ENOMEM;
 311
 312       memset (data, 0, sizeof (struct tsd_data));
 313       __gthread_set_tsd_data (tcb, data);
 314     }
 315
 316   generation = tsd_keys.generation[key];
 317
 318   if (generation & 1)
 319     return EINVAL;
 320
 321   data->generation[key] = generation;
 322   data->values[key] = value;
 323
 324   return 0;
 325 }