1 '\" te
2 .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved.
3 .\" Copyright 2016 Joyent, Inc.
4 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
5 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
6 .\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. 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
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
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
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
|
1 '\" te
2 .\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved.
3 .\" Copyright 2016 Joyent, Inc.
4 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
5 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
6 .\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. 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 .nf
13 gcc -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ]
14 .fi
15
16 .LP
17 .nf
18 #include <pthread.h>
19 .fi
20
21 .SS "C11"
22 .nf
23 gcc -std=c11 -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ]
24 .fi
25
26 .LP
27 .nf
28 #include <threads.h>
29 .fi
30
31 .SS "illumos"
32 .nf
33 gcc -D_REENTRANT [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ]
34 .fi
35
36 .LP
37 .nf
38 #include <sched.h>
39 .fi
40
41 .LP
42 .nf
43 #include <thread.h>
44 .fi
45
46 .SH DESCRIPTION
47 A thread is an independent source of execution within a process. Every process
48 is created with a single thread, which calls the
49 .B main
50 function. A process may have multiple threads, all of which are scheduled
51 independently by the system and may run concurrently. Threads within a process
52 all use the same address space and as a result can access all data in the
53 process; however, each thread is created with its own attributes and its own
54 stack. When a thread is created, it inherits the signal mask of the thread which
55 created it, but it has no pending signals.
56 .sp
57 .LP
58 All threads of execution have their own, independent life time, though it is
59 ultimately bounded by the life time of the process. If the process terminates
60 for any reason, whether due to a call to \fBexit\fR(3C), the receipt of a fatal
61 signal, or some other reason, then all threads within the process are
62 terminated. Threads may themselves exit and status information of them may be
63 obtained, for more information, see the \fBpthread_detach\fR(3C),
64 \fBpthread_join\fR(3C), and \fBpthread_exit\fR(3C) functions, and their
65 equivalents as described in the tables later on in the manual.
66 .sp
67 .LP
68 Most hardware platforms do not have any special synchronization for data objects
69 which may be accessed concurrently from multiple threads of execution. To avoid
70 such problems, programs may use atomic operations (see \fBatomic_ops\fR(3C)) and
71 locking primitives, such as mutexes, readers/writer locks, condition variables,
72 and semaphores. Note, that depending on the hardware platform, memory
73 synchronization may be necessary, for more information, see \fBmembar_ops\fR(3C).
74 .LP
75 POSIX, C11, and illumos threads each have their own implementation within
76 \fBlibc\fR(3LIB). All implementations are interoperable, their functionality
77 similar, and can be used within the same application. Only POSIX threads are
78 guaranteed to be fully portable to other POSIX-compliant environments. C11
79 threads are an optional part of ISO C11 and may not exist on every ISO C11
80 platform. POSIX, C11, and illumos threads require different source and include
81 files. See \fBSYNOPSIS\fR.
82 .SS "Similarities"
83 Most of the POSIX and illumos threading functions have counterparts with each
84 other. POSIX function names, with the exception of the semaphore names, have a
85 "\fBpthread\fR" prefix. Function names for similar POSIX and illumos functions
86 have similar endings. Typically, similar POSIX and illumos functions have the
87 same number and use of arguments.
88 .SS "Differences"
89 POSIX pthreads and illumos threads differ in the following ways:
90 .RS +4
91 .TP
92 .ie t \(bu
93 .el o
94 POSIX threads are more portable.
95 .RE
96 .RS +4
97 .TP
98 .ie t \(bu
99 .el o
100 POSIX threads establish characteristics for each thread according to
101 configurable attribute objects.
102 .RE
103 .RS +4
104 .TP
105 .ie t \(bu
106 .el o
107 POSIX pthreads implement thread cancellation.
108 .RE
115 .RS +4
116 .TP
117 .ie t \(bu
118 .el o
119 POSIX pthreads allow for clean-up handlers for \fBfork\fR(2) calls.
120 .RE
121 .RS +4
122 .TP
123 .ie t \(bu
124 .el o
125 illumos threads can be suspended and continued.
126 .RE
127 .RS +4
128 .TP
129 .ie t \(bu
130 .el o
131 illumos threads implement daemon threads, for whose demise the process does not
132 wait.
133 .RE
134 .SS "Comparison to C11 Threads"
135 C11 threads are not as functional as either POSIX or illumos threads. C11
136 threads only support intra-process locking and do not have any form of
137 readers/writer locking or semaphores. In general, POSIX threads will be more
138 portable than C11 threads, all POSIX-compliant systems support pthreads;
139 however, not all C environments support C11 Threads.
140 .sp
141 .LP
142 In addition to lacking other common synchronization primitives, the ISO/IEC
143 standard for C11 threads does not have rich error semantics. In an effort to not
144 extend the set of error numbers standardized in ISO/IEC C11, none of the
145 routines set errno and instead multiple distinguishable errors, aside from the
146 equivalent to ENOMEM and EBUSY, are all squashed into one. As such, users of the
147 platform are encouraged to use POSIX threads, unless a portability concern
148 dictates otherwise.
149
150 .SH FUNCTION COMPARISON
151 The following table compares the POSIX pthreads, C11 threads, and illumos
152 threads functions. When a comparable interface is not available either in POSIX
153 pthreads, C11 threads or illumos threads, a hyphen (\fB-\fR) appears in the
154 column.
155 .SS "Functions Related to Creation"
156
157 .TS
158 l l l
159 l l l .
160 \fBPOSIX\fR \fBillumos\fR \fBC11\fR
161 \fBpthread_create()\fR \fBthr_create()\fR \fBthrd_create()\fR
162 \fBpthread_attr_init()\fR \fB-\fR \fB-\fR
163 \fBpthread_attr_setdetachstate()\fR \fB-\fR \fB-\fR
164 \fBpthread_attr_getdetachstate()\fR \fB-\fR \fB-\fR
165 \fBpthread_attr_setinheritsched()\fR \fB-\fR \fB-\fR
166 \fBpthread_attr_getinheritsched()\fR \fB-\fR \fB-\fR
167 \fBpthread_attr_setschedparam()\fR \fB-\fR \fB-\fR
168 \fBpthread_attr_getschedparam()\fR \fB-\fR \fB-\fR
169 \fBpthread_attr_setschedpolicy()\fR \fB-\fR \fB-\fR
170 \fBpthread_attr_getschedpolicy()\fR \fB-\fR \fB-\fR
311 \fBpthread_rwlock_tryrdlock()\fR \fBrw_tryrdlock()\fR \fB-\fR
312 \fBpthread_rwlock_wrlock()\fR \fBrw_wrlock()\fR \fB-\fR
313 \fBpthread_rwlock_trywrlock()\fR \fBrw_trywrlock()\fR \fB-\fR
314 \fBpthread_rwlock_unlock()\fR \fBrw_unlock()\fR \fB-\fR
315 \fBpthread_rwlock_destroy()\fR \fBrwlock_destroy()\fR \fB-\fR
316 \fBpthread_rwlockattr_init()\fR \fB-\fR \fB-\fR
317 \fBpthread_rwlockattr_destroy()\fR \fB-\fR \fB-\fR
318 \fBpthread_rwlockattr_getpshared()\fR \fB-\fR \fB-\fR
319 \fBpthread_rwlockattr_setpshared()\fR \fB-\fR \fB-\fR
320 .TE
321
322 .SS "Functions Related to Semaphores"
323
324 .TS
325 l l l
326 l l l .
327 \fBPOSIX\fR \fBillumos\fR \fBC11\fR
328 \fBsem_init()\fR \fBsema_init()\fR \fB-\fR
329 \fBsem_open()\fR \fB-\fR \fB-\fR
330 \fBsem_close()\fR \fB-\fR \fB-\fR
331 \fBsem_wait()\fR \fBsema_wait()\fR \fB-\fR
332 \fBsem_trywait()\fR \fBsema_trywait()\fR \fB-\fR
333 \fBsem_post()\fR \fBsema_post()\fR \fB-\fR
334 \fBsem_getvalue()\fR \fB-\fR \fB-\fR
335 \fBsem_unlink()\fR \fB-\fR \fB-\fR
336 \fBsem_destroy()\fR \fBsema_destroy()\fR \fB-\fR
337 .TE
338
339 .SS "Functions Related to fork(\|) Clean Up"
340
341 .TS
342 l l l
343 l l l .
344 \fBPOSIX\fR \fBillumos\fR \fBC11\fR
345 \fBpthread_atfork()\fR \fB-\fR \fB-\fR
346 .TE
347
348 .SS "Functions Related to Limits"
349
350 .TS
351 l l l
352 l l l .
353 \fBPOSIX\fR \fBillumos\fR \fBC11\fR
354 \fBpthread_once()\fR \fB-\fR \fBcall_once()\fR
355 .TE
356
357 .SS "Functions Related to Debugging"
358
359 .TS
360 l l l
361 l l l .
362 \fBPOSIX\fR \fBillumos\fR \fBC11\fR
363 \fB-\fR \fBthr_stksegment()\fR \fB-\fR
364 .TE
365
366 .SH LOCKING
367 .SS "Synchronization"
368 Multithreaded behavior is asynchronous, and therefore, optimized for
369 concurrent and parallel processing. As threads, always from within the same
370 process and sometimes from multiple processes, share global data with each
371 other, they are not guaranteed exclusive access to the shared data at any point
372 in time. Securing mutually exclusive access to shared data requires
373 synchronization among the threads. Both POSIX and illumos implement four
374 synchronization mechanisms: mutexes, condition variables, reader/writer locking
375 (\fIoptimized frequent-read occasional-write mutex\fR), and semaphores, where as
376 C11 threads only implement two mechanisms: mutexes and condition variables.
377 .sp
378 .LP
379 Synchronizing multiple threads diminishes their concurrency. The coarser the
380 grain of synchronization, that is, the larger the block of code that is locked,
381 the lesser the concurrency.
382 .SS "MT \fBfork()\fR"
383 If a threads program calls \fBfork\fR(2), it implicitly calls \fBfork1\fR(2),
384 which replicates only the calling thread. Should there be any outstanding
385 mutexes throughout the process, the application should call
386 \fBpthread_atfork\fR(3C) to wait for and acquire those mutexes prior to calling
387 \fBfork()\fR.
388 .SH SCHEDULING
389 .SS "POSIX Threads"
390 illumos supports the following three POSIX scheduling policies:
391 .sp
392 .ne 2
393 .na
394 \fB\fBSCHED_OTHER\fR\fR
395 .ad
396 .RS 15n
397 Traditional Timesharing scheduling policy. It is based on the timesharing (TS)
398 scheduling class.
399 .RE
400
401 .sp
402 .ne 2
403 .na
404 \fB\fBSCHED_FIFO\fR\fR
405 .ad
406 .RS 15n
407 First-In-First-Out scheduling policy. Threads scheduled to this policy, if not
408 preempted by a higher priority, will proceed until completion. Such threads are
409 in real-time (RT) scheduling class. The calling process must have a effective
440 .ne 2
441 .na
442 \fB\fBSCHED_FSS\fR\fR
443 .ad
444 .RS 13n
445 Threads are scheduled according to the Fair-Share Class (FSS) policy as
446 described in \fBpriocntl\fR(2).
447 .RE
448
449 .sp
450 .ne 2
451 .na
452 \fB\fBSCHED_FX\fR\fR
453 .ad
454 .RS 13n
455 Threads are scheduled according to the Fixed-Priority Class (FX) policy as
456 described in \fBpriocntl\fR(2).
457 .RE
458
459 .SS "illumos Threads"
460 Only scheduling policy supported is \fBSCHED_OTHER\fR, which is timesharing,
461 based on the \fBTS\fR scheduling class.
462 .SH ERRORS
463 In a multithreaded application, \fBEINTR\fR can be returned from blocking
464 system calls when another thread calls \fBforkall\fR(2).
465 .SH USAGE
466 .SS "\fB-mt\fR compiler option"
467 The \fB-mt\fR compiler option compiles and links for multithreaded code. It
468 compiles source files with \(mi\fBD_REENTRANT\fR and augments the set of
469 support libraries properly.
470 .sp
471 .LP
472 Users of other compilers such as gcc and clang should manually set
473 \(mi\fBD_REENTRANT\fR on the compilation line. There are no other libraries or
474 flags necessary.
475 .SH ATTRIBUTES
476 See \fBattributes\fR(5) for descriptions of the following attributes:
477 .sp
478
479 .sp
480 .TS
481 box;
482 c | c
483 l | l .
484 ATTRIBUTE TYPE ATTRIBUTE VALUE
485 _
486 MT-Level MT-Safe, Fork 1-Safe
487 .TE
488
489 .SH SEE ALSO
490 \fBcrle\fR(1), \fBfork\fR(2), \fBpriocntl\fR(2), \fBlibpthread\fR(3LIB),
491 \fBlibrt\fR(3LIB), \fBlibthread\fR(3LIB), \fBpthread_atfork\fR(3C),
492 \fBpthread_create\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
493 .sp
494 .LP
495 \fILinker and Libraries Guide\fR
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