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annotate BlockingQueue.c @ 30:e59d39874274

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Compiles, but does not yet run properly
author Some Random Person <seanhalle@yahoo.com>
date Tue, 13 Mar 2012 10:07:00 -0700
parents bd38feb38c80
children b66352de717e d01d48b023ca
rev   line source
Me@19 1 /*
Me@19 2 * Copyright 2009 OpenSourceStewardshipFoundation.org
Me@19 3 * Licensed under GNU General Public License version 2
Me@19 4 *
Me@19 5 * Author: seanhalle@yahoo.com
Me@19 6 */
Me@19 7
Me@19 8
Me@19 9 #include <stdio.h>
Me@19 10 #include <errno.h>
Me@19 11 #include <pthread.h>
Me@19 12 #include <stdlib.h>
Me@19 13 #include <sched.h>
seanhalle@29 14 #include <string.h>
Me@19 15
Me@19 16 #include "BlockingQueue.h"
Me@19 17
Me@19 18 #define INC(x) (++x == 1024) ? (x) = 0 : (x)
Me@19 19
Me@19 20 #define SPINLOCK_TRIES 100000
Me@19 21
Me@19 22
Me@19 23
Me@19 24 //===========================================================================
Me@19 25 // multi reader multi writer fast Q via CAS
Me@19 26 #ifndef _GNU_SOURCE
Me@19 27 #define _GNU_SOURCE
Me@19 28
Me@19 29 /*This is a blocking queue, but it uses CAS instr plus yield() when empty
Me@19 30 * or full
Me@19 31 *It uses CAS because it's meant to have more than one reader and more than
Me@19 32 * one writer.
Me@19 33 */
Me@19 34
Me@19 35 CASQueueStruc* makeCASQ()
Me@19 36 {
Me@19 37 CASQueueStruc* retQ;
seanhalle@27 38 retQ = (CASQueueStruc *) VMS_WL__malloc( sizeof( CASQueueStruc ) );
Me@19 39
Me@19 40 retQ->insertLock = UNLOCKED;
Me@19 41 retQ->extractLock= UNLOCKED;
seanhalle@29 42
seanhalle@29 43 retQ->extractPos = (volatile void**)&(retQ->startOfData[0]); //side by side == empty
seanhalle@29 44 retQ->insertPos = (volatile void**)&(retQ->startOfData[1]); // so start pos's have to be
Me@19 45 retQ->endOfData = &(retQ->startOfData[1023]);
Me@19 46
Me@19 47 return retQ;
Me@19 48 }
Me@19 49
Me@19 50
Me@19 51 void* readCASQ( CASQueueStruc* Q )
Me@19 52 { void *out = 0;
Me@19 53 int tries = 0;
Me@19 54 void **startOfData = Q->startOfData;
Me@19 55 void **endOfData = Q->endOfData;
Me@19 56
Me@19 57 int gotLock = FALSE;
Me@19 58
Me@19 59 while( TRUE )
Me@19 60 { //this intrinsic returns true if the lock held "UNLOCKED", in which
Me@19 61 // case it now holds "LOCKED" -- if it already held "LOCKED", then
Me@19 62 // gotLock is FALSE
Me@19 63 gotLock =
Me@19 64 __sync_bool_compare_and_swap( &(Q->extractLock), UNLOCKED, LOCKED );
Me@19 65 //NOTE: checked assy, and it does lock correctly..
Me@19 66 if( gotLock )
Me@19 67 {
seanhalle@29 68 void **insertPos = (void **)Q->insertPos;
seanhalle@29 69 void **extractPos = (void **)Q->extractPos;
Me@19 70
Me@19 71 //if not empty -- extract just below insert when empty
Me@19 72 if( insertPos - extractPos != 1 &&
Me@19 73 !(extractPos == endOfData && insertPos == startOfData))
Me@19 74 { //move before read
Me@19 75 if( extractPos == endOfData ) //write new pos exactly once, correctly
Me@19 76 { Q->extractPos = startOfData; //can't overrun then fix it 'cause
Me@19 77 } // other thread might read bad pos
Me@19 78 else
Me@19 79 { Q->extractPos++;
Me@19 80 }
seanhalle@29 81 out = (void *) *(Q->extractPos);
Me@19 82 Q->extractLock = UNLOCKED;
Me@19 83 return out;
Me@19 84 }
Me@19 85 else //Q is empty
Me@19 86 { Q->extractLock = UNLOCKED;//empty, so release lock for others
Me@19 87 }
Me@19 88 }
Me@19 89 //Q is busy or empty
Me@19 90 tries++;
Me@19 91 if( tries > SPINLOCK_TRIES ) pthread_yield(); //not reliable
Me@19 92 }
Me@19 93 }
Me@19 94
Me@19 95 void writeCASQ( void * in, CASQueueStruc* Q )
Me@19 96 {
Me@19 97 int tries = 0;
Me@19 98 //TODO: need to make Q volatile? Want to do this Q in assembly!
Me@19 99 //Have no idea what GCC's going to do to this code
Me@19 100 void **startOfData = Q->startOfData;
Me@19 101 void **endOfData = Q->endOfData;
Me@19 102
Me@19 103 int gotLock = FALSE;
Me@19 104
Me@19 105 while( TRUE )
Me@19 106 { //this intrinsic returns true if the lock held "UNLOCKED", in which
Me@19 107 // case it now holds "LOCKED" -- if it already held "LOCKED", then
Me@19 108 // gotLock is FALSE
Me@19 109 gotLock =
Me@19 110 __sync_bool_compare_and_swap( &(Q->insertLock), UNLOCKED, LOCKED );
Me@19 111 if( gotLock )
Me@19 112 {
seanhalle@29 113 void **insertPos = (void **)Q->insertPos;
seanhalle@29 114 void **extractPos = (void **)Q->extractPos;
Me@19 115
Me@19 116 //check if room to insert.. can't use a count variable
Me@19 117 // 'cause both insertor Thd and extractor Thd would write it
Me@19 118 if( extractPos - insertPos != 1 &&
Me@19 119 !(insertPos == endOfData && extractPos == startOfData))
Me@19 120 { *(Q->insertPos) = in; //insert before move
Me@19 121 if( insertPos == endOfData )
Me@19 122 { Q->insertPos = startOfData;
Me@19 123 }
Me@19 124 else
Me@19 125 { Q->insertPos++;
Me@19 126 }
Me@19 127 Q->insertLock = UNLOCKED;
Me@19 128 return;
Me@19 129 }
Me@19 130 else //Q is full
Me@19 131 { Q->insertLock = UNLOCKED;//full, so release lock for others
Me@19 132 }
Me@19 133 }
Me@19 134 tries++;
Me@19 135 if( tries > SPINLOCK_TRIES ) pthread_yield(); //not reliable
Me@19 136 }
Me@19 137 }
Me@19 138
Me@19 139 #endif //_GNU_SOURCE
Me@19 140
Me@19 141
Me@19 142 //===========================================================================
Me@19 143 //Single reader single writer super fast Q.. no atomic instrs..
Me@19 144
Me@19 145
Me@19 146 /*This is a blocking queue, but it uses no atomic instructions, just does
Me@19 147 * yield() when empty or full
Me@19 148 *
Me@19 149 *It doesn't need any atomic instructions because only a single thread
Me@19 150 * extracts and only a single thread inserts, and it has no locations that
Me@19 151 * are written by both. It writes before moving and moves before reading,
Me@19 152 * and never lets write position and read position be the same, so dis-
Me@19 153 * synchrony can only ever cause an unnecessary call to yield(), never a
Me@19 154 * wrong value (by monotonicity of movement of pointers, plus single writer
Me@19 155 * to pointers, plus sequence of write before change pointer, plus
Me@19 156 * assumptions that if thread A semantically writes X before Y, then thread
Me@19 157 * B will see the writes in that order.)
Me@19 158 */
Me@19 159
Me@19 160 SRSWQueueStruc* makeSRSWQ()
Me@19 161 {
Me@19 162 SRSWQueueStruc* retQ;
seanhalle@27 163 retQ = (SRSWQueueStruc *) VMS_WL__malloc( sizeof( SRSWQueueStruc ) );
Me@19 164 memset( retQ->startOfData, 0, 1024 * sizeof(void *) );
Me@19 165
Me@19 166 retQ->extractPos = &(retQ->startOfData[0]); //side by side == empty
Me@19 167 retQ->insertPos = &(retQ->startOfData[1]); // so start pos's have to be
Me@19 168 retQ->endOfData = &(retQ->startOfData[1023]);
Me@19 169
Me@19 170 return retQ;
Me@19 171 }
Me@19 172
Me@19 173 void
Me@19 174 freeSRSWQ( SRSWQueueStruc* Q )
Me@19 175 {
Me@22 176 VMS_int__free( Q );
Me@19 177 }
Me@19 178
Me@19 179 void* readSRSWQ( SRSWQueueStruc* Q )
Me@19 180 { void *out = 0;
Me@19 181 int tries = 0;
Me@19 182
Me@19 183 while( TRUE )
Me@19 184 {
Me@19 185 if( Q->insertPos - Q->extractPos != 1 &&
Me@19 186 !(Q->extractPos == Q->endOfData && Q->insertPos == Q->startOfData))
Me@19 187 { if( Q->extractPos >= Q->endOfData ) Q->extractPos = Q->startOfData;
Me@19 188 else Q->extractPos++; //move before read
Me@19 189 out = *(Q->extractPos);
Me@19 190 return out;
Me@19 191 }
Me@19 192 //Q is empty
Me@19 193 tries++;
Me@19 194 if( tries > SPINLOCK_TRIES ) pthread_yield();
Me@19 195 }
Me@19 196 }
Me@19 197
Me@19 198
Me@19 199 void* readSRSWQ_NonBlocking( SRSWQueueStruc* Q )
Me@19 200 { void *out = 0;
Me@19 201 int tries = 0;
Me@19 202
Me@19 203 while( TRUE )
Me@19 204 {
Me@19 205 if( Q->insertPos - Q->extractPos != 1 &&
Me@19 206 !(Q->extractPos == Q->endOfData && Q->insertPos == Q->startOfData))
Me@19 207 { Q->extractPos++; //move before read
Me@19 208 if( Q->extractPos > Q->endOfData ) Q->extractPos = Q->startOfData;
Me@19 209 out = *(Q->extractPos);
Me@19 210 return out;
Me@19 211 }
Me@19 212 //Q is empty
Me@19 213 tries++;
Me@19 214 if( tries > 10 ) return NULL; //long enough for writer to finish
Me@19 215 }
Me@19 216 }
Me@19 217
Me@19 218
Me@19 219 void writeSRSWQ( void * in, SRSWQueueStruc* Q )
Me@19 220 {
Me@19 221 int tries = 0;
Me@19 222
Me@19 223 while( TRUE )
Me@19 224 {
Me@19 225 if( Q->extractPos - Q->insertPos != 1 &&
Me@19 226 !(Q->insertPos == Q->endOfData && Q->extractPos == Q->startOfData))
Me@19 227 { *(Q->insertPos) = in; //insert before move
Me@19 228 if( Q->insertPos >= Q->endOfData ) Q->insertPos = Q->startOfData;
Me@19 229 else Q->insertPos++;
Me@19 230 return;
Me@19 231 }
Me@19 232 //Q is full
Me@19 233 tries++;
Me@19 234 if( tries > SPINLOCK_TRIES ) pthread_yield();
Me@19 235 }
Me@19 236 }
Me@19 237
Me@19 238
Me@19 239
Me@19 240 //===========================================================================
Me@19 241 //Single reader Multiple writer super fast Q.. no atomic instrs..
Me@19 242
Me@19 243
Me@19 244 /*This is a blocking queue, but it uses no atomic instructions, just does
Me@19 245 * yield() when empty or full
Me@19 246 *
Me@19 247 *It doesn't need any atomic instructions because only a single thread
Me@19 248 * extracts and only a single thread inserts, and it has no locations that
Me@19 249 * are written by both. It writes before moving and moves before reading,
Me@19 250 * and never lets write position and read position be the same, so dis-
Me@19 251 * synchrony can only ever cause an unnecessary call to yield(), never a
Me@19 252 * wrong value (by monotonicity of movement of pointers, plus single writer
Me@19 253 * to pointers, plus sequence of write before change pointer, plus
Me@19 254 * assumptions that if thread A semantically writes X before Y, then thread
Me@19 255 * B will see the writes in that order.)
Me@19 256 *
Me@19 257 *The multi-writer version is implemented as a hierarchy. Each writer has
Me@19 258 * its own single-reader single-writer queue. The reader simply does a
Me@19 259 * round-robin harvesting from them.
Me@19 260 *
Me@19 261 *A writer must first register itself with the queue, and receives an ID back
Me@19 262 * It then uses that ID on each write operation.
Me@19 263 *
Me@19 264 *The implementation is:
Me@19 265 *Physically:
Me@19 266 * -] the SRMWQueueStruc holds an array of SRSWQueueStruc s
Me@19 267 * -] it also has read-pointer to the last queue a write was taken from.
Me@19 268 *
Me@19 269 *Action-Patterns:
Me@19 270 * -] To add a writer
Me@19 271 * --]] writer-thread calls addWriterToQ(), remember the ID it returns
Me@19 272 * --]] internally addWriterToQ does:
Me@19 273 * ---]]] if needs more room, makes a larger writer-array
Me@19 274 * ---]]] copies the old writer-array into the new
Me@19 275 * ---]]] makes a new SRSW queue an puts it into the array
Me@19 276 * ---]]] returns the index to the new SRSW queue as the ID
Me@19 277 * -] To write
Me@19 278 * --]] writer thread calls writeSRMWQ, passing the Q struc and its writer-ID
Me@19 279 * --]] this call may block, via repeated yield() calls
Me@19 280 * --]] internally, writeSRMWQ does:
Me@19 281 * ---]]] uses the writerID as index to get the SRSW queue for that writer
Me@19 282 * ---]]] performs writeQ on that queue (may block via repeated yield calls)
Me@19 283 * -] To Read
Me@19 284 * --]] reader calls readSRMWQ, passing the Q struc
Me@19 285 * --]] this call may block, via repeated yield() calls
Me@19 286 * --]] internally, readSRMWQ does:
Me@19 287 * ---]]] gets saved index of last SRSW queue read from
Me@19 288 * ---]]] increments index and gets indexed queue
Me@19 289 * ---]]] does a non-blocking read of that queue
Me@19 290 * ---]]] if gets something, saves index and returns that value
Me@19 291 * ---]]] if gets null, then goes to next queue
Me@19 292 * ---]]] if got null from all the queues then does yield() then tries again
Me@19 293 *
Me@19 294 *Note: "0" is used as the value null, so SRSW queues must only contain
Me@19 295 * pointers, and cannot use 0 as a valid pointer value.
Me@19 296 *
Me@19 297 */
Me@19 298
Me@19 299 SRMWQueueStruc* makeSRMWQ()
Me@19 300 { SRMWQueueStruc* retQ;
Me@19 301
seanhalle@27 302 retQ = (SRMWQueueStruc *) VMS_WL__malloc( sizeof( SRMWQueueStruc ) );
Me@19 303
Me@19 304 retQ->numInternalQs = 0;
Me@19 305 retQ->internalQsSz = 10;
seanhalle@27 306 retQ->internalQs = VMS_WL__malloc( retQ->internalQsSz * sizeof(SRSWQueueStruc *));
Me@19 307
Me@19 308 retQ->lastQReadFrom = 0;
Me@19 309
Me@19 310 return retQ;
Me@19 311 }
Me@19 312
Me@19 313 /* ---]]] if needs more room, makes a larger writer-array
Me@19 314 * ---]]] copies the old writer-array into the new
Me@19 315 * ---]]] makes a new SRSW queue an puts it into the array
Me@19 316 * ---]]] returns the index to the new SRSW queue as the ID
Me@19 317 *
Me@19 318 *NOTE: assuming all adds are completed before any writes or reads are
Me@19 319 * performed.. otherwise, this needs to be re-done carefully, probably with
Me@19 320 * a lock.
Me@19 321 */
Me@19 322 int addWriterToSRMWQ( SRMWQueueStruc* Q )
Me@19 323 { int oldSz, i;
Me@19 324 SRSWQueueStruc * *oldArray;
Me@19 325
Me@19 326 (Q->numInternalQs)++;
Me@19 327 if( Q->numInternalQs >= Q->internalQsSz )
Me@19 328 { //full, so make bigger
Me@19 329 oldSz = Q->internalQsSz;
Me@19 330 oldArray = Q->internalQs;
Me@19 331 Q->internalQsSz *= 2;
seanhalle@27 332 Q->internalQs = VMS_WL__malloc( Q->internalQsSz * sizeof(SRSWQueueStruc *));
Me@19 333 for( i = 0; i < oldSz; i++ )
Me@19 334 { Q->internalQs[i] = oldArray[i];
Me@19 335 }
Me@22 336 VMS_int__free( oldArray );
Me@19 337 }
Me@19 338 Q->internalQs[ Q->numInternalQs - 1 ] = makeSRSWQ();
Me@19 339 return Q->numInternalQs - 1;
Me@19 340 }
Me@19 341
Me@19 342
Me@19 343 /* ---]]] gets saved index of last SRSW queue read-from
Me@19 344 * ---]]] increments index and gets indexed queue
Me@19 345 * ---]]] does a non-blocking read of that queue
Me@19 346 * ---]]] if gets something, saves index and returns that value
Me@19 347 * ---]]] if gets null, then goes to next queue
Me@19 348 * ---]]] if got null from all the queues then does yield() then tries again
Me@19 349 */
Me@19 350 void* readSRMWQ( SRMWQueueStruc* Q )
Me@19 351 { SRSWQueueStruc *readQ;
Me@19 352 void *readValue = 0;
Me@19 353 int tries = 0;
Me@19 354 int QToReadFrom = 0;
Me@19 355
Me@19 356 QToReadFrom = Q->lastQReadFrom;
Me@19 357
Me@19 358 while( TRUE )
Me@19 359 { QToReadFrom++;
Me@19 360 if( QToReadFrom >= Q->numInternalQs ) QToReadFrom = 0;
Me@19 361 readQ = Q->internalQs[ QToReadFrom ];
Me@19 362 readValue = readSRSWQ_NonBlocking( readQ );
Me@19 363
Me@19 364 if( readValue != 0 ) //got a value, return it
Me@19 365 { Q->lastQReadFrom = QToReadFrom;
Me@19 366 return readValue;
Me@19 367 }
Me@19 368 else //SRSW Q just read is empty
Me@19 369 { //check if all queues have been tried
Me@19 370 if( QToReadFrom == Q->lastQReadFrom ) //all the queues tried & empty
Me@19 371 { tries++; //give a writer a chance to finish before yield
Me@19 372 if( tries > SPINLOCK_TRIES ) pthread_yield();
Me@19 373 }
Me@19 374 }
Me@19 375 }
Me@19 376 }
Me@19 377
Me@19 378
Me@19 379 /*
Me@19 380 * ---]]] uses the writerID as index to get the SRSW queue for that writer
Me@19 381 * ---]]] performs writeQ on that queue (may block via repeated yield calls)
Me@19 382 */
Me@19 383 void writeSRMWQ( void * in, SRMWQueueStruc* Q, int writerID )
Me@19 384 {
Me@19 385 if( in == 0 ) printf( "error, wrote 0 to SRMW Q" );//TODO: throw an error
Me@19 386
Me@19 387 writeSRSWQ( in, Q->internalQs[ writerID ] );
Me@19 388 }