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