git.lttng.org Git - userspace-rcu.git/blob

   1 #define SINGLE_FLIP
   2
   3 #define NR_READERS 1
   4 #define NR_WRITERS 1
   5
   6 #define NR_PROCS 2
   7
   8
   9 #if (NR_READERS == 1)
  10
  11 #define read_free_race  (read_generation[0] == last_free_gen)
  12 #define read_free       (free_done && data_access[0])
  13
  14 #elif (NR_READERS == 2)
  15
  16 #define read_free_race  (read_generation[0] == last_free_gen || read_generation[1] == last_free_gen)
  17 #define read_free       (free_done && (data_access[0] || data_access[1]))
  18
  19 #else
  20
  21 #error "Too many readers"
  22
  23 #endif
  24
  25 #define RCU_GP_CTR_BIT (1 << 7)
  26 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
  27
  28 #ifndef READER_NEST_LEVEL
  29 #define READER_NEST_LEVEL 2
  30 #endif
  31
  32 #define REMOTE_BARRIERS
  33 /*
  34  * mem.spin: Promela code to validate memory barriers with OOO memory.
  35  *
  36  * This program is free software; you can redistribute it and/or modify
  37  * it under the terms of the GNU General Public License as published by
  38  * the Free Software Foundation; either version 2 of the License, or
  39  * (at your option) any later version.
  40  *
  41  * This program is distributed in the hope that it will be useful,
  42  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  43  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  44  * GNU General Public License for more details.
  45  *
  46  * You should have received a copy of the GNU General Public License
  47  * along with this program; if not, write to the Free Software
  48  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  49  *
  50  * Copyright (c) 2009 Mathieu Desnoyers
  51  */
  52
  53 /* Promela validation variables. */
  54
  55 /* specific defines "included" here */
  56 /* DEFINES file "included" here */
  57
  58 #define get_pid()       (_pid)
  59
  60 /*
  61  * Each process have its own data in cache. Caches are randomly updated.
  62  * smp_wmb and smp_rmb forces cache updates (write and read), smp_mb forces
  63  * both.
  64  */
  65
  66 typedef per_proc_byte {
  67         byte val[NR_PROCS];
  68 };
  69
  70 /* Bitfield has a maximum of 8 procs */
  71 typedef per_proc_bit {
  72         byte bitfield;
  73 };
  74
  75 #define DECLARE_CACHED_VAR(type, x)     \
  76         type mem_##x;                   \
  77         per_proc_##type cached_##x;     \
  78         per_proc_bit cache_dirty_##x;
  79
  80 #define INIT_CACHED_VAR(x, v, j)        \
  81         mem_##x = v;                    \
  82         cache_dirty_##x.bitfield = 0;   \
  83         j = 0;                          \
  84         do                              \
  85         :: j < NR_PROCS ->              \
  86                 cached_##x.val[j] = v;  \
  87                 j++                     \
  88         :: j >= NR_PROCS -> break       \
  89         od;
  90
  91 #define IS_CACHE_DIRTY(x, id)   (cache_dirty_##x.bitfield & (1 << id))
  92
  93 #define READ_CACHED_VAR(x)      (cached_##x.val[get_pid()])
  94
  95 #define WRITE_CACHED_VAR(x, v)                          \
  96         atomic {                                        \
  97                 cached_##x.val[get_pid()] = v;          \
  98                 cache_dirty_##x.bitfield =              \
  99                         cache_dirty_##x.bitfield | (1 << get_pid());    \
 100         }
 101
 102 #define CACHE_WRITE_TO_MEM(x, id)                       \
 103         if                                              \
 104         :: IS_CACHE_DIRTY(x, id) ->                     \
 105                 mem_##x = cached_##x.val[id];           \
 106                 cache_dirty_##x.bitfield =              \
 107                         cache_dirty_##x.bitfield & (~(1 << id));        \
 108         :: else ->                                      \
 109                 skip                                    \
 110         fi;
 111
 112 #define CACHE_READ_FROM_MEM(x, id)      \
 113         if                              \
 114         :: !IS_CACHE_DIRTY(x, id) ->    \
 115                 cached_##x.val[id] = mem_##x;\
 116         :: else ->                      \
 117                 skip                    \
 118         fi;
 119
 120 /*
 121  * May update other caches if cache is dirty, or not.
 122  */
 123 #define RANDOM_CACHE_WRITE_TO_MEM(x, id)\
 124         if                              \
 125         :: 1 -> CACHE_WRITE_TO_MEM(x, id);      \
 126         :: 1 -> skip                    \
 127         fi;
 128
 129 #define RANDOM_CACHE_READ_FROM_MEM(x, id)\
 130         if                              \
 131         :: 1 -> CACHE_READ_FROM_MEM(x, id);     \
 132         :: 1 -> skip                    \
 133         fi;
 134
 135 /*
 136  * Remote barriers tests the scheme where a signal (or IPI) is sent to all
 137  * reader threads to promote their compiler barrier to a smp_mb().
 138  */
 139 #ifdef REMOTE_BARRIERS
 140
 141 inline smp_rmb_pid(i, j)
 142 {
 143         atomic {
 144                 CACHE_READ_FROM_MEM(urcu_gp_ctr, i);
 145                 j = 0;
 146                 do
 147                 :: j < NR_READERS ->
 148                         CACHE_READ_FROM_MEM(urcu_active_readers[j], i);
 149                         j++
 150                 :: j >= NR_READERS -> break
 151                 od;
 152                 CACHE_READ_FROM_MEM(generation_ptr, i);
 153         }
 154 }
 155
 156 inline smp_wmb_pid(i, j)
 157 {
 158         atomic {
 159                 CACHE_WRITE_TO_MEM(urcu_gp_ctr, i);
 160                 j = 0;
 161                 do
 162                 :: j < NR_READERS ->
 163                         CACHE_WRITE_TO_MEM(urcu_active_readers[j], i);
 164                         j++
 165                 :: j >= NR_READERS -> break
 166                 od;
 167                 CACHE_WRITE_TO_MEM(generation_ptr, i);
 168         }
 169 }
 170
 171 inline smp_mb_pid(i, j)
 172 {
 173         atomic {
 174 #ifndef NO_WMB
 175                 smp_wmb_pid(i, j);
 176 #endif
 177 #ifndef NO_RMB
 178                 smp_rmb_pid(i, j);
 179 #endif
 180 #ifdef NO_WMB
 181 #ifdef NO_RMB
 182                 ooo_mem(i);
 183 #endif
 184 #endif
 185         }
 186 }
 187
 188 /*
 189  * Readers do a simple barrier(), writers are doing a smp_mb() _and_ sending a
 190  * signal or IPI to have all readers execute a smp_mb.
 191  * We are not modeling the whole rendez-vous between readers and writers here,
 192  * we just let the writer update each reader's caches remotely.
 193  */
 194 inline smp_mb(i, j)
 195 {
 196         if
 197         :: get_pid() >= NR_READERS ->
 198                 smp_mb_pid(get_pid(), j);
 199                 i = 0;
 200                 do
 201                 :: i < NR_READERS ->
 202                         smp_mb_pid(i, j);
 203                         i++;
 204                 :: i >= NR_READERS -> break
 205                 od;
 206                 smp_mb_pid(get_pid(), j);
 207         :: else -> skip;
 208         fi;
 209 }
 210
 211 #else
 212
 213 inline smp_rmb(i, j)
 214 {
 215         atomic {
 216                 CACHE_READ_FROM_MEM(urcu_gp_ctr, get_pid());
 217                 i = 0;
 218                 do
 219                 :: i < NR_READERS ->
 220                         CACHE_READ_FROM_MEM(urcu_active_readers[i], get_pid());
 221                         i++
 222                 :: i >= NR_READERS -> break
 223                 od;
 224                 CACHE_READ_FROM_MEM(generation_ptr, get_pid());
 225         }
 226 }
 227
 228 inline smp_wmb(i, j)
 229 {
 230         atomic {
 231                 CACHE_WRITE_TO_MEM(urcu_gp_ctr, get_pid());
 232                 i = 0;
 233                 do
 234                 :: i < NR_READERS ->
 235                         CACHE_WRITE_TO_MEM(urcu_active_readers[i], get_pid());
 236                         i++
 237                 :: i >= NR_READERS -> break
 238                 od;
 239                 CACHE_WRITE_TO_MEM(generation_ptr, get_pid());
 240         }
 241 }
 242
 243 inline smp_mb(i, j)
 244 {
 245         atomic {
 246 #ifndef NO_WMB
 247                 smp_wmb(i, j);
 248 #endif
 249 #ifndef NO_RMB
 250                 smp_rmb(i, j);
 251 #endif
 252 #ifdef NO_WMB
 253 #ifdef NO_RMB
 254                 ooo_mem(i);
 255 #endif
 256 #endif
 257         }
 258 }
 259
 260 #endif
 261
 262 /* Keep in sync manually with smp_rmb, wmp_wmb, ooo_mem and init() */
 263 DECLARE_CACHED_VAR(byte, urcu_gp_ctr);
 264 /* Note ! currently only two readers */
 265 DECLARE_CACHED_VAR(byte, urcu_active_readers[NR_READERS]);
 266 /* pointer generation */
 267 DECLARE_CACHED_VAR(byte, generation_ptr);
 268
 269 byte last_free_gen = 0;
 270 bit free_done = 0;
 271 byte read_generation[NR_READERS];
 272 bit data_access[NR_READERS];
 273
 274 bit write_lock = 0;
 275
 276 bit init_done = 0;
 277
 278 inline wait_init_done()
 279 {
 280         do
 281         :: init_done == 0 -> skip;
 282         :: else -> break;
 283         od;
 284 }
 285
 286 inline ooo_mem(i)
 287 {
 288         atomic {
 289                 RANDOM_CACHE_WRITE_TO_MEM(urcu_gp_ctr, get_pid());
 290                 i = 0;
 291                 do
 292                 :: i < NR_READERS ->
 293                         RANDOM_CACHE_WRITE_TO_MEM(urcu_active_readers[i],
 294                                 get_pid());
 295                         i++
 296                 :: i >= NR_READERS -> break
 297                 od;
 298                 RANDOM_CACHE_WRITE_TO_MEM(generation_ptr, get_pid());
 299                 RANDOM_CACHE_READ_FROM_MEM(urcu_gp_ctr, get_pid());
 300                 i = 0;
 301                 do
 302                 :: i < NR_READERS ->
 303                         RANDOM_CACHE_READ_FROM_MEM(urcu_active_readers[i],
 304                                 get_pid());
 305                         i++
 306                 :: i >= NR_READERS -> break
 307                 od;
 308                 RANDOM_CACHE_READ_FROM_MEM(generation_ptr, get_pid());
 309         }
 310 }
 311
 312 #define get_readerid()  (get_pid())
 313 #define get_writerid()  (get_readerid() + NR_READERS)
 314
 315 inline wait_for_reader(tmp, tmp2, i, j)
 316 {
 317         do
 318         :: 1 ->
 319                 tmp2 = READ_CACHED_VAR(urcu_active_readers[tmp]);
 320                 ooo_mem(i);
 321                 if
 322                 :: (tmp2 & RCU_GP_CTR_NEST_MASK)
 323                         && ((tmp2 ^ READ_CACHED_VAR(urcu_gp_ctr))
 324                                 & RCU_GP_CTR_BIT) ->
 325 #ifndef GEN_ERROR_WRITER_PROGRESS
 326                         smp_mb(i, j);
 327 #else
 328                         ooo_mem(i);
 329 #endif
 330                 :: else ->
 331                         break;
 332                 fi;
 333         od;
 334 }
 335
 336 inline wait_for_quiescent_state(tmp, tmp2, i, j)
 337 {
 338         tmp = 0;
 339         do
 340         :: tmp < NR_READERS ->
 341                 wait_for_reader(tmp, tmp2, i, j);
 342                 if
 343                 :: (NR_READERS > 1) && (tmp < NR_READERS - 1)
 344                         -> ooo_mem(i);
 345                 :: else
 346                         -> skip;
 347                 fi;
 348                 tmp++
 349         :: tmp >= NR_READERS -> break
 350         od;
 351 }
 352
 353 /* Model the RCU read-side critical section. */
 354
 355 inline urcu_one_read(i, j, nest_i, tmp, tmp2)
 356 {
 357         nest_i = 0;
 358         do
 359         :: nest_i < READER_NEST_LEVEL ->
 360                 ooo_mem(i);
 361                 tmp = READ_CACHED_VAR(urcu_active_readers[get_readerid()]);
 362                 ooo_mem(i);
 363                 if
 364                 :: (!(tmp & RCU_GP_CTR_NEST_MASK))
 365                         ->
 366                         tmp2 = READ_CACHED_VAR(urcu_gp_ctr);
 367                         ooo_mem(i);
 368                         WRITE_CACHED_VAR(urcu_active_readers[get_readerid()],
 369                                          tmp2);
 370                 :: else ->
 371                         WRITE_CACHED_VAR(urcu_active_readers[get_readerid()],
 372                                          tmp + 1);
 373                 fi;
 374                 smp_mb(i, j);
 375                 nest_i++;
 376         :: nest_i >= READER_NEST_LEVEL -> break;
 377         od;
 378
 379         ooo_mem(i);
 380         read_generation[get_readerid()] = READ_CACHED_VAR(generation_ptr);
 381         ooo_mem(i);
 382         data_access[get_readerid()] = 1;
 383         ooo_mem(i);
 384         data_access[get_readerid()] = 0;
 385
 386         nest_i = 0;
 387         do
 388         :: nest_i < READER_NEST_LEVEL ->
 389                 smp_mb(i, j);
 390                 tmp2 = READ_CACHED_VAR(urcu_active_readers[get_readerid()]);
 391                 ooo_mem(i);
 392                 WRITE_CACHED_VAR(urcu_active_readers[get_readerid()], tmp2 - 1);
 393                 nest_i++;
 394         :: nest_i >= READER_NEST_LEVEL -> break;
 395         od;
 396         ooo_mem(i);
 397         //smp_mc(i);    /* added */
 398 }
 399
 400 active [NR_READERS] proctype urcu_reader()
 401 {
 402         byte i, j, nest_i;
 403         byte tmp, tmp2;
 404
 405         wait_init_done();
 406
 407         assert(get_pid() < NR_PROCS);
 408
 409 end_reader:
 410         do
 411         :: 1 ->
 412                 /*
 413                  * We do not test reader's progress here, because we are mainly
 414                  * interested in writer's progress. The reader never blocks
 415                  * anyway. We have to test for reader/writer's progress
 416                  * separately, otherwise we could think the writer is doing
 417                  * progress when it's blocked by an always progressing reader.
 418                  */
 419 #ifdef READER_PROGRESS
 420                 /* Only test progress of one random reader. They are all the
 421                  * same. */
 422                 atomic {
 423                         if
 424                         :: get_readerid() == 0 ->
 425 progress_reader:
 426                                 skip;
 427                         :: else ->
 428                                 skip;
 429                         fi;
 430                 }
 431 #endif
 432                 urcu_one_read(i, j, nest_i, tmp, tmp2);
 433         od;
 434 }
 435
 436 /* Model the RCU update process. */
 437
 438 active proctype urcu_writer()
 439 {
 440         byte i, j;
 441         byte tmp, tmp2;
 442         byte old_gen;
 443
 444         wait_init_done();
 445
 446         assert(get_pid() < NR_PROCS);
 447
 448         do
 449         :: (READ_CACHED_VAR(generation_ptr) < 5) ->
 450 #ifdef WRITER_PROGRESS
 451 progress_writer1:
 452 #endif
 453                 ooo_mem(i);
 454                 atomic {
 455                         old_gen = READ_CACHED_VAR(generation_ptr);
 456                         WRITE_CACHED_VAR(generation_ptr, old_gen + 1);
 457                 }
 458                 ooo_mem(i);
 459
 460                 do
 461                 :: 1 ->
 462                         atomic {
 463                                 if
 464                                 :: write_lock == 0 ->
 465                                         write_lock = 1;
 466                                         break;
 467                                 :: else ->
 468                                         skip;
 469                                 fi;
 470                         }
 471                 od;
 472                 smp_mb(i, j);
 473                 tmp = READ_CACHED_VAR(urcu_gp_ctr);
 474                 ooo_mem(i);
 475                 WRITE_CACHED_VAR(urcu_gp_ctr, tmp ^ RCU_GP_CTR_BIT);
 476                 ooo_mem(i);
 477                 //smp_mc(i);
 478                 wait_for_quiescent_state(tmp, tmp2, i, j);
 479                 //smp_mc(i);
 480 #ifndef SINGLE_FLIP
 481                 ooo_mem(i);
 482                 tmp = READ_CACHED_VAR(urcu_gp_ctr);
 483                 ooo_mem(i);
 484                 WRITE_CACHED_VAR(urcu_gp_ctr, tmp ^ RCU_GP_CTR_BIT);
 485                 //smp_mc(i);
 486                 ooo_mem(i);
 487                 wait_for_quiescent_state(tmp, tmp2, i, j);
 488 #endif
 489                 smp_mb(i, j);
 490                 write_lock = 0;
 491                 /* free-up step, e.g., kfree(). */
 492                 atomic {
 493                         last_free_gen = old_gen;
 494                         free_done = 1;
 495                 }
 496         :: else -> break;
 497         od;
 498         /*
 499          * Given the reader loops infinitely, let the writer also busy-loop
 500          * with progress here so, with weak fairness, we can test the
 501          * writer's progress.
 502          */
 503 end_writer:
 504         do
 505         :: 1 ->
 506 #ifdef WRITER_PROGRESS
 507 progress_writer2:
 508 #endif
 509                 skip;
 510         od;
 511 }
 512
 513 /* Leave after the readers and writers so the pid count is ok. */
 514 init {
 515         byte i, j;
 516
 517         atomic {
 518                 INIT_CACHED_VAR(urcu_gp_ctr, 1, j);
 519                 INIT_CACHED_VAR(generation_ptr, 0, j);
 520
 521                 i = 0;
 522                 do
 523                 :: i < NR_READERS ->
 524                         INIT_CACHED_VAR(urcu_active_readers[i], 0, j);
 525                         read_generation[i] = 1;
 526                         data_access[i] = 0;
 527                         i++;
 528                 :: i >= NR_READERS -> break
 529                 od;
 530                 init_done = 1;
 531         }
 532 }