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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] 7 .TH THREADS 5 "Mar 27, 2016" 8 .SH NAME 9 threads, pthreads \- POSIX pthreads, c11, and illumos threads concepts 10 .SH SYNOPSIS 11 .SS "POSIX" 12 .LP 13 .nf 14 gcc -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ] 15 .fi 16 17 .LP 18 .nf 19 #include <pthread.h> 20 .fi 21 22 .SS "C11" 23 .LP 24 .nf 25 gcc -std=c11 -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ] 26 .fi 27 28 .LP 29 .nf 30 #include <threads.h> 31 .fi 32 33 .SS "illumos" 34 .LP 35 .nf 36 gcc -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ] 37 .fi 38 39 .LP 40 .nf 41 #include <sched.h> 42 .fi 43 44 .LP 45 .nf 46 #include <thread.h> 47 .fi 48 49 .SH DESCRIPTION 50 .LP 51 A thread is an independent source of execution within a process. Every process 52 is created with a single thread, which calls the 53 .B main 54 function. A process may have multiple threads, all of which are scheduled 55 independently by the system and may run concurrently. Threads within a process 56 all use the same address space and as a result can access all data in the 57 process; however, each thread is created with its own attributes and its own 58 stack. When a thread is created, it inherits the signal mask of the thread which 59 created it, but it has no pending signals. 60 .sp 61 .LP 62 All threads of execution have their own, independent life time, though it is 63 ultimately bounded by the life time of the process. If the process terminates 64 for any reason, whether due to a call to \fBexit\fR(3C), the receipt of a fatal 65 signal, or some other reason, then all threads within the process are 66 terminated. Threads may themselves exit and status information of them may be 67 obtained, for more information, see the \fBpthread_detach\fR(3C), 68 \fBpthread_join\fR(3C), and \fBpthread_exit\fR(3C) functions, and their 69 equivalents as described in the tables later on in the manual. 70 .sp 71 .LP 72 Most hardware platforms do not have any special synchronization for data objects 73 which may be accessed concurrently from multiple threads of execution. To avoid 74 such problems, programs may use atomic operations (see \fBatomic_ops\fR(3C)) and 75 locking primitives, such as mutexes, readers/writer locks, condition variables, 76 and semaphores. Note, that depending on the hardware platform, memory 77 synchronization may be necessary, for more information, see \fBmembar_ops\fR(3C). 78 .LP 79 POSIX, C11, and illumos threads each have their own implementation within 80 \fBlibc\fR(3LIB). All implementations are interoperable, their functionality 81 similar, and can be used within the same application. Only POSIX threads are 82 guaranteed to be fully portable to other POSIX-compliant environments. C11 83 threads are an optional part of ISO C11 and may not exist on every ISO C11 84 platform. POSIX, C11, and illumos threads require different source and include 85 files. See \fBSYNOPSIS\fR. 86 .SS "Similarities" 87 .LP 88 Most of the POSIX and illumos threading functions have counterparts with each 89 other. POSIX function names, with the exception of the semaphore names, have a 90 "\fBpthread\fR" prefix. Function names for similar POSIX and illumos functions 91 have similar endings. Typically, similar POSIX and illumos functions have the 92 same number and use of arguments. 93 .SS "Differences" 94 .LP 95 POSIX pthreads and illumos threads differ in the following ways: 96 .RS +4 97 .TP 98 .ie t \(bu 99 .el o 100 POSIX threads are more portable. 101 .RE 102 .RS +4 103 .TP 104 .ie t \(bu 105 .el o 106 POSIX threads establish characteristics for each thread according to 107 configurable attribute objects. 108 .RE 109 .RS +4 110 .TP 111 .ie t \(bu 112 .el o 113 POSIX pthreads implement thread cancellation. 114 .RE 115 .RS +4 116 .TP 117 .ie t \(bu 118 .el o 119 POSIX pthreads enforce scheduling algorithms. 120 .RE 121 .RS +4 122 .TP 123 .ie t \(bu 124 .el o 125 POSIX pthreads allow for clean-up handlers for \fBfork\fR(2) calls. 126 .RE 127 .RS +4 128 .TP 129 .ie t \(bu 130 .el o 131 illumos threads can be suspended and continued. 132 .RE 133 .RS +4 134 .TP 135 .ie t \(bu 136 .el o 137 illumos threads implement daemon threads, for whose demise the process does not 138 wait. 139 .RE 140 .SS "Comparison to C11 Threads" 141 .LP 142 C11 threads are not as functional as either POSIX or illumos threads. C11 143 threads only support intra-process locking and do not have any form of 144 readers/writer locking or semaphores. In general, POSIX threads will be more 145 portable than C11 threads, all POSIX-compliant systems support pthreads; 146 however, not all C environments support C11 Threads. 147 .sp 148 .LP 149 In addition to lacking other common synchronization primitives, the ISO/IEC 150 standard for C11 threads does not have rich error semantics. In an effort to not 151 extend the set of error numbers standardized in ISO/IEC C11, none of the 152 routines set errno and instead multiple distinguishable errors, aside from the 153 equivalent to ENOMEM and EBUSY, are all squashed into one. As such, users of the 154 platform are encouraged to use POSIX threads, unless a portability concern 155 dictates otherwise. 156 157 .SH FUNCTION COMPARISON 158 .LP 159 The following table compares the POSIX pthreads, C11 threads, and illumos 160 threads functions. When a comparable interface is not available either in POSIX 161 pthreads, C11 threads or illumos threads, a hyphen (\fB-\fR) appears in the 162 column. 163 .SS "Functions Related to Creation" 164 165 .TS 166 l l l 167 l l l . 168 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 169 \fBpthread_create()\fR \fBthr_create()\fR \fBthrd_create()\fR 170 \fBpthread_attr_init()\fR \fB-\fR \fB-\fR 171 \fBpthread_attr_setdetachstate()\fR \fB-\fR \fB-\fR 172 \fBpthread_attr_getdetachstate()\fR \fB-\fR \fB-\fR 173 \fBpthread_attr_setinheritsched()\fR \fB-\fR \fB-\fR 174 \fBpthread_attr_getinheritsched()\fR \fB-\fR \fB-\fR 175 \fBpthread_attr_setschedparam()\fR \fB-\fR \fB-\fR 176 \fBpthread_attr_getschedparam()\fR \fB-\fR \fB-\fR 177 \fBpthread_attr_setschedpolicy()\fR \fB-\fR \fB-\fR 178 \fBpthread_attr_getschedpolicy()\fR \fB-\fR \fB-\fR 179 \fBpthread_attr_setscope()\fR \fB-\fR \fB-\fR 180 \fBpthread_attr_getscope()\fR \fB-\fR \fB-\fR 181 \fBpthread_attr_setstackaddr()\fR \fB-\fR \fB-\fR 182 \fBpthread_attr_getstackaddr()\fR \fB-\fR \fB-\fR 183 \fBpthread_attr_setstacksize()\fR \fB-\fR \fB-\fR 184 \fBpthread_attr_getstacksize()\fR \fB-\fR \fB-\fR 185 \fBpthread_attr_getguardsize()\fR \fB-\fR \fB-\fR 186 \fBpthread_attr_setguardsize()\fR \fB-\fR \fB-\fR 187 \fBpthread_attr_destroy()\fR \fB-\fR \fB-\fR 188 \fB-\fR \fBthr_min_stack()\fR \fB-\fR 189 .TE 190 191 .SS "Functions Related to Exit" 192 193 .TS 194 l l l 195 l l l . 196 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 197 \fBpthread_exit()\fR \fBthr_exit()\fR \fBthrd_exit()\fR 198 \fBpthread_join()\fR \fBthr_join()\fR \fBthrd_join()\fR 199 \fBpthread_detach()\fR \fB-\fR \fBthrd_detach()\fR 200 .TE 201 202 .SS "Functions Related to Thread Specific Data" 203 204 .TS 205 l l l 206 l l l . 207 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 208 \fBpthread_key_create()\fR \fBthr_keycreate()\fR \fBtss_create()\fR 209 \fBpthread_setspecific()\fR \fBthr_setspecific()\fR \fBtss_set()\fR 210 \fBpthread_getspecific()\fR \fBthr_getspecific()\fR \fBtss_get()\fR 211 \fBpthread_key_delete()\fR \fB-\fR \fBtss_delete()\fR 212 .TE 213 214 .SS "Functions Related to Signals" 215 216 .TS 217 l l l 218 l l l . 219 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 220 \fBpthread_sigmask()\fR \fBthr_sigsetmask()\fR \fB-\fR 221 \fBpthread_kill()\fR \fBthr_kill()\fR \fB-\fR 222 .TE 223 224 .SS "Functions Related to IDs" 225 226 .TS 227 l l l 228 l l l . 229 \fBPOSIX\fR \fBillumos\fR \fBc11\fR 230 \fBpthread_self()\fR \fBthr_self()\fR \fBthrd_current()\fR 231 \fBpthread_equal()\fR \fB-\fR \fBthrd_equal()\fR 232 \fB-\fR \fBthr_main()\fR \fB-\fR 233 .TE 234 235 .SS "Functions Related to Scheduling" 236 237 .TS 238 l l l 239 l l l . 240 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 241 \fB-\fR \fBthr_yield()\fR \fBthrd_yield()\fR 242 \fB-\fR \fBthr_suspend()\fR \fB-\fR 243 \fB-\fR \fBthr_continue()\fR \fB-\fR 244 \fBpthread_setconcurrency()\fR \fBthr_setconcurrency()\fR \fB-\fR 245 \fBpthread_getconcurrency()\fR \fBthr_getconcurrency()\fR \fB-\fR 246 \fBpthread_setschedparam()\fR \fBthr_setprio()\fR \fB-\fR 247 \fBpthread_setschedprio()\fR \fBthr_setprio()\fR \fB-\fR 248 \fBpthread_getschedparam()\fR \fBthr_getprio()\fR \fB-\fR 249 .TE 250 251 .SS "Functions Related to Cancellation" 252 253 .TS 254 l l l 255 l l l . 256 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 257 \fBpthread_cancel()\fR \fB-\fR \fB-\fR 258 \fBpthread_setcancelstate()\fR \fB-\fR \fB-\fR 259 \fBpthread_setcanceltype()\fR \fB-\fR \fB-\fR 260 \fBpthread_testcancel()\fR \fB-\fR \fB-\fR 261 \fBpthread_cleanup_pop()\fR \fB-\fR \fB-\fR 262 \fBpthread_cleanup_push()\fR \fB-\fR \fB-\fR 263 .TE 264 265 .SS "Functions Related to Mutexes" 266 267 .TS 268 l l l 269 l l l . 270 \fBPOSIX\fR \fBillumos\fR \fBc11\fR 271 \fBpthread_mutex_init()\fR \fBmutex_init()\fR \fBmtx_init()\fR 272 \fBpthread_mutexattr_init()\fR \fB-\fR \fB-\fR 273 \fBpthread_mutexattr_setpshared()\fR \fB-\fR \fB-\fR 274 \fBpthread_mutexattr_getpshared()\fR \fB-\fR \fB-\fR 275 \fBpthread_mutexattr_setprotocol()\fR \fB-\fR \fB-\fR 276 \fBpthread_mutexattr_getprotocol()\fR \fB-\fR \fB-\fR 277 \fBpthread_mutexattr_setprioceiling()\fR \fB-\fR \fB-\fR 278 \fBpthread_mutexattr_getprioceiling()\fR \fB-\fR \fB-\fR 279 \fBpthread_mutexattr_settype()\fR \fB-\fR \fB-\fR 280 \fBpthread_mutexattr_gettype()\fR \fB-\fR \fB-\fR 281 \fBpthread_mutexattr_setrobust()\fR \fB-\fR \fB-\fR 282 \fBpthread_mutexattr_getrobust()\fR \fB-\fR \fB-\fR 283 \fBpthread_mutexattr_destroy()\fR \fB-\fR \fBmtx_destroy()\fR 284 \fBpthread_mutex_setprioceiling()\fR \fB-\fR \fB-\fR 285 \fBpthread_mutex_getprioceiling()\fR \fB-\fR \fB-\fR 286 \fBpthread_mutex_lock()\fR \fBmutex_lock()\fR \fBmtx_lock()\fR 287 \fBpthread_mutex_timedlock()\fR \fB-\fR \fBmtx_timedlock()\fR 288 \fBpthread_mutex_trylock()\fR \fBmutex_trylock()\fR \fBmtx_trylock()\fR 289 \fBpthread_mutex_unlock()\fR \fBmutex_unlock()\fR \fBmtx_unlcok()\fR 290 \fBpthread_mutex_destroy()\fR \fBmutex_destroy()\fR \fBmtx_destroy()\fR 291 .TE 292 293 .SS "Functions Related to Condition Variables" 294 295 .TS 296 l l l 297 l l l . 298 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 299 \fBpthread_cond_init()\fR \fBcond_init()\fR \fBcnd_init()\fR 300 \fBpthread_condattr_init()\fR \fB-\fR \fB-\fR 301 \fBpthread_condattr_setpshared()\fR \fB-\fR \fB-\fR 302 \fBpthread_condattr_getpshared()\fR \fB-\fR \fB-\fR 303 \fBpthread_condattr_destroy()\fR \fB-\fR \fB-\fR 304 \fBpthread_cond_wait()\fR \fBcond_wait()\fR \fBcnd_wait()\fR 305 \fBpthread_cond_timedwait()\fR \fBcond_timedwait()\fR \fBcond_timedwait()\fR 306 \fBpthread_cond_signal()\fR \fBcond_signal()\fR \fBcnd_signal()\fR 307 \fBpthread_cond_broadcast()\fR \fBcond_broadcast()\fR \fBcnd_broadcast()\fR 308 \fBpthread_cond_destroy()\fR \fBcond_destroy()\fR \fBcnd_destroy()\fR 309 .TE 310 311 .SS "Functions Related to Reader/Writer Locking" 312 313 .TS 314 l l l 315 l l l . 316 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 317 \fBpthread_rwlock_init()\fR \fBrwlock_init()\fR \fB-\fR 318 \fBpthread_rwlock_rdlock()\fR \fBrw_rdlock()\fR \fB-\fR 319 \fBpthread_rwlock_tryrdlock()\fR \fBrw_tryrdlock()\fR \fB-\fR 320 \fBpthread_rwlock_wrlock()\fR \fBrw_wrlock()\fR \fB-\fR 321 \fBpthread_rwlock_trywrlock()\fR \fBrw_trywrlock()\fR \fB-\fR 322 \fBpthread_rwlock_unlock()\fR \fBrw_unlock()\fR \fB-\fR 323 \fBpthread_rwlock_destroy()\fR \fBrwlock_destroy()\fR \fB-\fR 324 \fBpthread_rwlockattr_init()\fR \fB-\fR \fB-\fR 325 \fBpthread_rwlockattr_destroy()\fR \fB-\fR \fB-\fR 326 \fBpthread_rwlockattr_getpshared()\fR \fB-\fR \fB-\fR 327 \fBpthread_rwlockattr_setpshared()\fR \fB-\fR \fB-\fR 328 .TE 329 330 .SS "Functions Related to Semaphores" 331 332 .TS 333 l l l 334 l l l . 335 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 336 \fBsem_init()\fR \fBsema_init()\fR \fB-\fR 337 \fBsem_open()\fR \fB-\fR \fB-\fR 338 \fBsem_close()\fR \fB-\fR \fB-\fR 339 \fBsem_wait()\fR \fBsema_wait()\ \fB-\fR 340 \fBsem_trywait()\fR \fBsema_trywait()\fR \fB-\fR 341 \fBsem_post()\fR \fBsema_post()\fR \fB-\fR 342 \fBsem_getvalue()\fR \fB-\fR \fB-\fR 343 \fBsem_unlink()\fR \fB-\fR \fB-\fR 344 \fBsem_destroy()\fR \fBsema_destroy()\fR \fB-\fR 345 .TE 346 347 .SS "Functions Related to fork(\|) Clean Up" 348 349 .TS 350 l l l 351 l l l . 352 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 353 \fBpthread_atfork()\fR \fB-\fR \fB-\fR 354 .TE 355 356 .SS "Functions Related to Limits" 357 358 .TS 359 l l l 360 l l l . 361 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 362 \fBpthread_once()\fR \fB-\fR \fBcall_once()\fR 363 .TE 364 365 .SS "Functions Related to Debugging" 366 367 .TS 368 l l l 369 l l l . 370 \fBPOSIX\fR \fBillumos\fR \fBC11\fR 371 \fB-\fR \fBthr_stksegment()\fR \fB-\fR 372 .TE 373 374 .SH LOCKING 375 .SS "Synchronization" 376 .LP 377 Multithreaded behavior is asynchronous, and therefore, optimized for 378 concurrent and parallel processing. As threads, always from within the same 379 process and sometimes from multiple processes, share global data with each 380 other, they are not guaranteed exclusive access to the shared data at any point 381 in time. Securing mutually exclusive access to shared data requires 382 synchronization among the threads. Both POSIX and illumos implement four 383 synchronization mechanisms: mutexes, condition variables, reader/writer locking 384 (\fIoptimized frequent-read occasional-write mutex\fR), and semaphores, where as 385 C11 threads only implement two mechanisms: mutexes and condition variables. 386 .sp 387 .LP 388 Synchronizing multiple threads diminishes their concurrency. The coarser the 389 grain of synchronization, that is, the larger the block of code that is locked, 390 the lesser the concurrency. 391 .SS "MT \fBfork()\fR" 392 .LP 393 If a threads program calls \fBfork\fR(2), it implicitly calls \fBfork1\fR(2), 394 which replicates only the calling thread. Should there be any outstanding 395 mutexes throughout the process, the application should call 396 \fBpthread_atfork\fR(3C) to wait for and acquire those mutexes prior to calling 397 \fBfork()\fR. 398 .SH SCHEDULING 399 .SS "POSIX Threads" 400 .LP 401 illumos supports the following three POSIX scheduling policies: 402 .sp 403 .ne 2 404 .na 405 \fB\fBSCHED_OTHER\fR\fR 406 .ad 407 .RS 15n 408 Traditional Timesharing scheduling policy. It is based on the timesharing (TS) 409 scheduling class. 410 .RE 411 412 .sp 413 .ne 2 414 .na 415 \fB\fBSCHED_FIFO\fR\fR 416 .ad 417 .RS 15n 418 First-In-First-Out scheduling policy. Threads scheduled to this policy, if not 419 preempted by a higher priority, will proceed until completion. Such threads are 420 in real-time (RT) scheduling class. The calling process must have a effective 421 user \fBID\fR of \fB0\fR. 422 .RE 423 424 .sp 425 .ne 2 426 .na 427 \fB\fBSCHED_RR\fR\fR 428 .ad 429 .RS 15n 430 Round-Robin scheduling policy. Threads scheduled to this policy, if not 431 preempted by a higher priority, will execute for a time period determined by 432 the system. Such threads are in real-time (RT) scheduling class and the calling 433 process must have a effective user \fBID\fR of \fB0\fR. 434 .RE 435 436 .sp 437 .LP 438 In addition to the POSIX-specified scheduling policies above, illumos also 439 supports these scheduling policies: 440 .sp 441 .ne 2 442 .na 443 \fB\fBSCHED_IA\fR\fR 444 .ad 445 .RS 13n 446 Threads are scheduled according to the Inter-Active Class (IA) policy as 447 described in \fBpriocntl\fR(2). 448 .RE 449 450 .sp 451 .ne 2 452 .na 453 \fB\fBSCHED_FSS\fR\fR 454 .ad 455 .RS 13n 456 Threads are scheduled according to the Fair-Share Class (FSS) policy as 457 described in \fBpriocntl\fR(2). 458 .RE 459 460 .sp 461 .ne 2 462 .na 463 \fB\fBSCHED_FX\fR\fR 464 .ad 465 .RS 13n 466 Threads are scheduled according to the Fixed-Priority Class (FX) policy as 467 described in \fBpriocntl\fR(2). 468 .RE 469 470 .SS "illumos Threads" 471 .LP 472 Only scheduling policy supported is \fBSCHED_OTHER\fR, which is timesharing, 473 based on the \fBTS\fR scheduling class. 474 .SH ERRORS 475 .LP 476 In a multithreaded application, \fBEINTR\fR can be returned from blocking 477 system calls when another thread calls \fBforkall\fR(2). 478 .SH USAGE 479 .SS "\fB-mt\fR compiler option" 480 .LP 481 The \fB-mt\fR compiler option compiles and links for multithreaded code. It 482 compiles source files with \(mi\fBD_REENTRANT\fR and augments the set of 483 support libraries properly. 484 .sp 485 .LP 486 Users of other compilers such as gcc and clang should manually set 487 \(mi\fBD_REENTRANT\fR on the compilation line. There are no other libraries or 488 flags necessary. 489 .SH ATTRIBUTES 490 .LP 491 See \fBattributes\fR(5) for descriptions of the following attributes: 492 .sp 493 494 .sp 495 .TS 496 box; 497 c | c 498 l | l . 499 ATTRIBUTE TYPE ATTRIBUTE VALUE 500 _ 501 MT-Level MT-Safe, Fork 1-Safe 502 .TE 503 504 .SH SEE ALSO 505 .LP 506 \fBcrle\fR(1), \fBfork\fR(2), \fBpriocntl\fR(2), \fBlibpthread\fR(3LIB), 507 \fBlibrt\fR(3LIB), \fBlibthread\fR(3LIB), \fBpthread_atfork\fR(3C), 508 \fBpthread_create\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5) 509 .sp 510 .LP 511 \fILinker and Libraries Guide\fR