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a2dab6bc | 1 | NOTE: This documentation describes the style of threading that was |
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2 | available in Perl 5.005. Perl 5.6.0 introduced the early beginnings of |
3 | interpreter-based threads support, also known as ithreads, and in Perl | |
4 | 5.8.0 the interpeter threads became available from perl level through | |
5 | the threads and threads::shared modules (in Perl 5.6 ithreads are | |
6 | available only internally and to XS extension builders, and used | |
7 | by the Win32 port for emulating fork()). | |
8 | ||
9 | If you really want the older support for threads described below, | |
10 | it is enabled with: | |
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11 | |
12 | sh Configure -Dusethreads -Duse5005threads | |
13 | ||
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14 | Be warned that the old 5.005 implementation of threads is known |
15 | to be quite buggy, and unmaintained, which means that the bugs | |
16 | are there to stay. (We are not mean by not fixing the bugs: | |
17 | the bugs are just really, really, really hard to fix. Honest.) | |
18 | ||
a2dab6bc | 19 | The rest of this document only applies to the use5005threads style of |
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20 | threads, and the comments on what works on which platform are highly |
21 | obsolete and preserved here for archaeology buffs only. The | |
22 | architecture specific hints files do all the necessary option | |
23 | tweaking automatically during Configure, both for the 5.005 threads | |
24 | and for the new interpreter threads. | |
25 | ||
a2dab6bc | 26 | --------------------------------------------------------------------------- |
99ed61e6 | 27 | |
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28 | Support for threading is still in the highly experimental stages. There |
29 | are known race conditions that show up under high contention on SMP | |
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30 | machines. Internal implementation is still subject to changes. |
31 | It is not recommended for production use at this time. | |
32 | ||
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33 | --------------------------------------------------------------------------- |
34 | ||
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35 | Building |
36 | ||
effcca5c | 37 | If your system is in the following list you should be able to just: |
e2198c6b | 38 | |
a2dab6bc | 39 | ./Configure -Dusethreads -Duse5005threads -des |
effcca5c | 40 | make |
69ce17de | 41 | |
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42 | and ignore the rest of this "Building" section. If not, continue |
43 | from the "Problems" section. | |
69ce17de | 44 | |
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45 | * Linux 2.* (with the LinuxThreads library installed: |
46 | that's the linuxthreads and linuxthreads-devel RPMs | |
47 | for RedHat) | |
3cec1e99 | 48 | |
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49 | * Tru64 UNIX (formerly Digital UNIX formerly DEC OSF/1) |
50 | (see additional note below) | |
69ce17de | 51 | |
effcca5c | 52 | * Solaris 2.* for recentish x (2.5 is OK) |
69ce17de | 53 | |
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54 | * IRIX 6.2 or newer. 6.2 will require a few OS patches. |
55 | IMPORTANT: Without patch 2401 (or its replacement), | |
56 | a kernel bug in IRIX 6.2 will cause your machine to | |
57 | panic and crash when running threaded perl. | |
58 | IRIX 6.3 and up should be OK. See lower down for patch details. | |
e2198c6b | 59 | |
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60 | * AIX 4.1.5 or newer. |
61 | ||
62 | * FreeBSD 2.2.8 or newer. | |
63 | ||
64 | * OpenBSD | |
65 | ||
f556e5b9 | 66 | * NeXTstep, OpenStep |
e2198c6b | 67 | |
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68 | * OS/2 |
69 | ||
70 | * DOS DJGPP | |
71 | ||
72 | * VM/ESA | |
73 | ||
74 | --------------------------------------------------------------------------- | |
75 | ||
76 | Problems | |
77 | ||
78 | If the simple way doesn't work or you are using another platform which | |
79 | you believe supports POSIX.1c threads then read on. Additional | |
80 | information may be in a platform-specific "hints" file in the hints/ | |
81 | subdirectory. | |
82 | ||
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83 | On platforms that use Configure to build perl, omit the -d from your |
84 | ./Configure arguments. For example, use: | |
e2198c6b | 85 | |
a2dab6bc | 86 | ./Configure -Dusethreads -Duse5005threads |
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87 | |
88 | When Configure prompts you for ccflags, insert any other arguments in | |
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89 | there that your compiler needs to use POSIX threads (-D_REENTRANT, |
90 | -pthreads, -threads, -pthread, -thread, are good guesses). When | |
91 | Configure prompts you for linking flags, include any flags required | |
92 | for threading (usually nothing special is required here). Finally, | |
93 | when Configure prompts you for libraries, include any necessary | |
94 | libraries (e.g. -lpthread). Pay attention to the order of libraries. | |
95 | It is probably necessary to specify your threading library *before* | |
96 | your standard C library, e.g. it might be necessary to have -lpthread | |
97 | -lc, instead of -lc -lpthread. You may also need to use -lc_r instead | |
effcca5c | 98 | of -lc. |
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99 | |
100 | Once you have specified all your compiler flags, you can have Configure | |
101 | accept all the defaults for the remainder of the session by typing &-d | |
102 | at any Configure prompt. | |
103 | ||
104 | Some additional notes (some of these may be obsolete now, other items | |
105 | may be handled automatically): | |
106 | ||
72aaf631 | 107 | For Digital Unix 4.x: |
e2198c6b | 108 | Add -pthread to ccflags |
72aaf631 | 109 | Add -pthread to ldflags |
d81a1b93 | 110 | Add -lpthread -lc_r to lddlflags |
e2198c6b | 111 | |
72aaf631 | 112 | For some reason, the extra includes for pthreads make Digital UNIX |
210b36aa | 113 | complain fatally about the sbrk() declaration in perl's malloc.c |
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114 | so use the native malloc, e.g. sh Configure -Uusemymalloc, or |
115 | manually edit your config.sh as follows: | |
116 | Change usemymalloc to n | |
117 | Zap mallocobj and mallocsrc (foo='') | |
118 | Change d_mymalloc to undef | |
119 | ||
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120 | For Digital Unix 3.x (Formerly DEC OSF/1): |
121 | Add -DOLD_PTHREADS_API to ccflags | |
effcca5c | 122 | If compiling with the GNU cc compiler, remove -threads from ccflags |
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123 | |
124 | (The following should be done automatically if you call Configure | |
125 | with the -Dusethreads option). | |
126 | Add -lpthread -lmach -lc_r to libs (in the order specified). | |
127 | ||
eb1cfdd6 | 128 | For IRIX: |
e2198c6b | 129 | (This should all be done automatically by the hint file). |
eb1cfdd6 | 130 | Add -lpthread to libs |
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131 | For IRIX 6.2, you have to have the following patches installed: |
132 | 1404 Irix 6.2 Posix 1003.1b man pages | |
133 | 1645 IRIX 6.2 & 6.3 POSIX header file updates | |
134 | 2000 Irix 6.2 Posix 1003.1b support modules | |
135 | 2254 Pthread library fixes | |
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136 | 2401 6.2 all platform kernel rollup |
137 | IMPORTANT: Without patch 2401, a kernel bug in IRIX 6.2 will | |
138 | cause your machine to panic and crash when running threaded perl. | |
139 | IRIX 6.3 and up should be OK. | |
140 | ||
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141 | For IRIX 6.3 and 6.4 the pthreads should work out of the box. |
142 | Thanks to Hannu Napari <Hannu.Napari@hut.fi> for the IRIX | |
143 | pthreads patches information. | |
effcca5c | 144 | |
ce637636 | 145 | For AIX: |
e2198c6b | 146 | (This should all be done automatically by the hint file). |
ce637636 | 147 | Change cc to xlc_r or cc_r. |
e2198c6b | 148 | Add -DNEED_PTHREAD_INIT to ccflags and cppflags |
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149 | Add -lc_r to libswanted |
150 | Change -lc in lddflags to be -lpthread -lc_r -lc | |
72aaf631 | 151 | |
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152 | For Win32: |
153 | See README.win32, and the notes at the beginning of win32/Makefile | |
154 | or win32/makefile.mk. | |
155 | ||
72aaf631 | 156 | Now you can do a |
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157 | make |
158 | ||
effcca5c | 159 | When you succeed in compiling and testing ("make test" after your |
210b36aa | 160 | build) a threaded Perl in a platform previously unknown to support |
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161 | threaded perl, please let perlbug@perl.com know about your victory. |
162 | Explain what you did in painful detail. | |
163 | ||
164 | --------------------------------------------------------------------------- | |
72aaf631 | 165 | |
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166 | O/S specific bugs |
167 | ||
e2198c6b | 168 | Irix 6.2: See the Irix warning above. |
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169 | |
170 | LinuxThreads 0.5 has a bug which can cause file descriptor 0 to be | |
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171 | closed after a fork() leading to many strange symptoms. Version 0.6 |
172 | has this fixed but the following patch can be applied to 0.5 for now: | |
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173 | |
174 | ----------------------------- cut here ----------------------------- | |
175 | --- linuxthreads-0.5/pthread.c.ORI Mon Oct 6 13:55:50 1997 | |
176 | +++ linuxthreads-0.5/pthread.c Mon Oct 6 13:57:24 1997 | |
177 | @@ -312,8 +312,10 @@ | |
178 | free(pthread_manager_thread_bos); | |
179 | pthread_manager_thread_bos = pthread_manager_thread_tos = NULL; | |
180 | /* Close the two ends of the pipe */ | |
181 | - close(pthread_manager_request); | |
182 | - close(pthread_manager_reader); | |
183 | + if (pthread_manager_request >= 0) { | |
184 | + close(pthread_manager_request); | |
185 | + close(pthread_manager_reader); | |
186 | + } | |
187 | pthread_manager_request = pthread_manager_reader = -1; | |
188 | /* Update the pid of the main thread */ | |
189 | self->p_pid = getpid(); | |
190 | ----------------------------- cut here ----------------------------- | |
191 | ||
192 | ||
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193 | Building the Thread extension |
194 | ||
5756a3ac | 195 | The Thread extension is now part of the main perl distribution tree. |
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196 | If you did Configure -Dusethreads -Duse5005threads then it will have been |
197 | added to the list of extensions automatically. | |
72aaf631 | 198 | |
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199 | You can try some of the tests with |
200 | cd ext/Thread | |
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201 | perl create.t |
202 | perl join.t | |
203 | perl lock.t | |
204 | perl io.t | |
205 | etc. | |
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206 | The io one leaves a thread reading from the keyboard on stdin so |
207 | as the ping messages appear you can type lines and see them echoed. | |
208 | ||
209 | Try running the main perl test suite too. There are known | |
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210 | failures for some of the DBM/DB extensions (if their underlying |
211 | libraries were not compiled to be thread-aware). | |
72aaf631 | 212 | |
effcca5c | 213 | --------------------------------------------------------------------------- |
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214 | |
215 | Bugs | |
216 | ||
72aaf631 | 217 | * FAKE_THREADS should produce a working perl but the Thread |
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218 | extension won't build with it yet. (FAKE_THREADS has not been |
219 | tested at all in recent times.) | |
72aaf631 | 220 | |
5756a3ac | 221 | * There may still be races where bugs show up under contention. |
72aaf631 | 222 | |
effcca5c | 223 | --------------------------------------------------------------------------- |
72aaf631 | 224 | |
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225 | Debugging |
226 | ||
8b73bbec | 227 | Use the -DS command-line option to turn on debugging of the |
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228 | multi-threading code. Under Linux, that also turns on a quick |
229 | hack I did to grab a bit of extra information from segfaults. | |
230 | If you have a fancier gdb/threads setup than I do then you'll | |
231 | have to delete the lines in perl.c which say | |
4d1ff10f | 232 | #if defined(DEBUGGING) && defined(USE_5005THREADS) && defined(__linux__) |
8b73bbec | 233 | DEBUG_S(signal(SIGSEGV, (void(*)(int))catch_sigsegv);); |
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234 | #endif |
235 | ||
effcca5c | 236 | --------------------------------------------------------------------------- |
1304aa9d | 237 | |
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238 | Background |
239 | ||
240 | Some old globals (e.g. stack_sp, op) and some old per-interpreter | |
241 | variables (e.g. tmps_stack, cxstack) move into struct thread. | |
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242 | All fields of struct thread which derived from original perl |
243 | variables have names of the form Tfoo. For example, stack_sp becomes | |
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244 | the field Tstack_sp of struct thread. For those fields which moved |
245 | from original perl, thread.h does | |
246 | #define foo (thr->Tfoo) | |
247 | This means that all functions in perl which need to use one of these | |
248 | fields need an (automatic) variable thr which points at the current | |
249 | thread's struct thread. For pp_foo functions, it is passed around as | |
250 | an argument, for other functions they do | |
251 | dTHR; | |
252 | which declares and initialises thr from thread-specific data | |
253 | via pthread_getspecific. If a function fails to compile with an | |
254 | error about "no such variable thr", it probably just needs a dTHR | |
255 | at the top. | |
256 | ||
257 | ||
258 | Fake threads | |
259 | ||
260 | For FAKE_THREADS, thr is a global variable and perl schedules threads | |
261 | by altering thr in between appropriate ops. The next and prev fields | |
262 | of struct thread keep all fake threads on a doubly linked list and | |
263 | the next_run and prev_run fields keep all runnable threads on a | |
264 | doubly linked list. Mutexes are stubs for FAKE_THREADS. Condition | |
265 | variables are implemented as a list of waiting threads. | |
266 | ||
267 | ||
268 | Mutexes and condition variables | |
269 | ||
270 | The API is via macros MUTEX_{INIT,LOCK,UNLOCK,DESTROY} and | |
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271 | COND_{INIT,WAIT,SIGNAL,BROADCAST,DESTROY}. |
272 | ||
273 | A mutex is only required to be a simple, fast mutex (e.g. it does not | |
274 | have to be recursive). It is only ever held across very short pieces | |
275 | of code. Condition variables are only ever signalled/broadcast while | |
276 | their associated mutex is held. (This constraint simplifies the | |
277 | implementation of condition variables in certain porting situations.) | |
278 | For POSIX threads, perl mutexes and condition variables correspond to | |
279 | POSIX ones. For FAKE_THREADS, mutexes are stubs and condition variables | |
210b36aa | 280 | are implemented as lists of waiting threads. For FAKE_THREADS, a thread |
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281 | waits on a condition variable by removing itself from the runnable |
282 | list, calling SCHEDULE to change thr to the next appropriate | |
283 | runnable thread and returning op (i.e. the new threads next op). | |
284 | This means that fake threads can only block while in PP code. | |
285 | A PP function which contains a COND_WAIT must be prepared to | |
286 | handle such restarts and can use the field "private" of struct | |
287 | thread to record its state. For fake threads, COND_SIGNAL and | |
288 | COND_BROADCAST work by putting back all the threads on the | |
289 | condition variables list into the run queue. Note that a mutex | |
290 | must *not* be held while returning from a PP function. | |
291 | ||
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292 | Perl locks and condition variables are both implemented as a |
293 | condpair_t structure, containing a mutex, an "owner" condition | |
294 | variable, an owner thread field and another condition variable). | |
295 | The structure is attached by 'm' magic to any SV. pp_lock locks | |
296 | such an object by waiting on the ownercond condition variable until | |
297 | the owner field is zero and then setting the owner field to its own | |
298 | thread pointer. The lock is semantically recursive so if the owner | |
299 | field already matches the current thread then pp_lock returns | |
300 | straight away. If the owner field has to be filled in then | |
301 | unlock_condpair is queued as an end-of-block destructor and | |
302 | that function zeroes out the owner field and signals the ownercond | |
303 | condition variable, thus waking up any other thread that wants to | |
304 | lock it. When used as a condition variable, the condpair is locked | |
305 | (involving the above wait-for-ownership and setting the owner field) | |
306 | and the spare condition variable field is used for waiting on. | |
307 | ||
308 | ||
309 | Thread states | |
310 | ||
311 | ||
312 | $t->join | |
313 | R_JOINABLE ---------------------> R_JOINED >----\ | |
314 | | \ pthread_join(t) | ^ | | |
315 | | \ | | join | pthread_join | |
316 | | \ | | | | |
317 | | \ | \------/ | |
318 | | \ | | |
319 | | \ | | |
320 | | $t->detach\ pthread_detach | | |
321 | | _\| | | |
322 | ends| R_DETACHED ends | unlink | |
323 | | \ | | |
324 | | ends \ unlink | | |
325 | | \ | | |
326 | | \ | | |
327 | | \ | | |
328 | | \ | | |
329 | | \ | | |
330 | V join detach _\| V | |
331 | ZOMBIE ----------------------------> DEAD | |
332 | pthread_join pthread_detach | |
333 | and unlink and unlink | |
334 | ||
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335 | |
336 | ||
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337 | Malcolm Beattie |
338 | mbeattie@sable.ox.ac.uk | |
69ce17de | 339 | Last updated: 27 November 1997 |
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340 | |
341 | Configure-related info updated 16 July 1998 by | |
342 | Andy Dougherty <doughera@lafayette.edu> | |
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343 | |
344 | Other minor updates 10 Feb 1999 by | |
345 | Gurusamy Sarathy | |
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346 | |
347 | More platforms added 26 Jul 1999 by | |
348 | Jarkko Hietaniemi |