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2 | '\" Copyright (c) 1999 Scriptics Corporation | |
3 | '\" Copyright (c) 1998 Sun Microsystems, Inc. | |
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8 | '\" RCS: @(#) $Id: Thread.3,v 1.14.2.2 2004/11/25 15:48:52 vasiljevic Exp $ | |
9 | '\" | |
10 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
11 | '\" manual entries. | |
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206 | '\" # SO - start of list of standard options | |
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208 | .SH "STANDARD OPTIONS" | |
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214 | '\" # SE - end of list of standard options | |
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219 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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226 | Command-Line Name: \\fB\\$1\\fR | |
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244 | \\$1\l'|0\(ul'\\$2 | |
245 | .. | |
246 | .TH Threads 3 "8.1" Tcl "Tcl Library Procedures" | |
247 | .BS | |
248 | .SH NAME | |
249 | Tcl_ConditionNotify, Tcl_ConditionWait, Tcl_ConditionFinalize, Tcl_GetThreadData, Tcl_MutexLock, Tcl_MutexUnlock, Tcl_MutexFinalize, Tcl_CreateThread, Tcl_JoinThread \- Tcl thread support. | |
250 | .SH SYNOPSIS | |
251 | .nf | |
252 | \fB#include <tcl.h>\fR | |
253 | .sp | |
254 | void | |
255 | \fBTcl_ConditionNotify\fR(\fIcondPtr\fR) | |
256 | .sp | |
257 | void | |
258 | \fBTcl_ConditionWait\fR(\fIcondPtr, mutexPtr, timePtr\fR) | |
259 | .sp | |
260 | void | |
261 | \fBTcl_ConditionFinalize\fR(\fIcondPtr\fR) | |
262 | .sp | |
263 | Void * | |
264 | \fBTcl_GetThreadData\fR(\fIkeyPtr, size\fR) | |
265 | .sp | |
266 | void | |
267 | \fBTcl_MutexLock\fR(\fImutexPtr\fR) | |
268 | .sp | |
269 | void | |
270 | \fBTcl_MutexUnlock\fR(\fImutexPtr\fR) | |
271 | .sp | |
272 | void | |
273 | \fBTcl_MutexFinalize\fR(\fImutexPtr\fR) | |
274 | .sp | |
275 | int | |
276 | \fBTcl_CreateThread\fR(\fIidPtr, threadProc, clientData, stackSize, flags\fR) | |
277 | .sp | |
278 | int | |
279 | \fBTcl_JoinThread\fR(\fIid, result\fR) | |
280 | .SH ARGUMENTS | |
281 | .AS Tcl_ThreadDataKey *keyPtr | |
282 | .AP Tcl_Condition *condPtr in | |
283 | A condition variable, which must be associated with a mutex lock. | |
284 | .AP Tcl_Mutex *mutexPtr in | |
285 | A mutex lock. | |
286 | .AP Tcl_Time *timePtr in | |
287 | A time limit on the condition wait. NULL to wait forever. | |
288 | Note that a polling value of 0 seconds doesn't make much sense. | |
289 | .AP Tcl_ThreadDataKey *keyPtr in | |
290 | This identifies a block of thread local storage. The key should be | |
291 | static and process-wide, yet each thread will end up associating | |
292 | a different block of storage with this key. | |
293 | .AP int *size in | |
294 | The size of the thread local storage block. This amount of data | |
295 | is allocated and initialized to zero the first time each thread | |
296 | calls \fBTcl_GetThreadData\fR. | |
297 | .AP Tcl_ThreadId *idPtr out | |
298 | The referred storage will contain the id of the newly created thread as | |
299 | returned by the operating system. | |
300 | .AP Tcl_ThreadId id in | |
301 | Id of the thread waited upon. | |
302 | .AP Tcl_ThreadCreateProc threadProc in | |
303 | This procedure will act as the \fBmain()\fR of the newly created | |
304 | thread. The specified \fIclientData\fR will be its sole argument. | |
305 | .AP ClientData clientData in | |
306 | Arbitrary information. Passed as sole argument to the \fIthreadProc\fR. | |
307 | .AP int stackSize in | |
308 | The size of the stack given to the new thread. | |
309 | .AP int flags in | |
310 | Bitmask containing flags allowing the caller to modify behaviour of | |
311 | the new thread. | |
312 | .AP int *result out | |
313 | The referred storage is used to place the exit code of the thread | |
314 | waited upon into it. | |
315 | .BE | |
316 | .SH INTRODUCTION | |
317 | Beginning with the 8.1 release, the Tcl core is thread safe, which | |
318 | allows you to incorporate Tcl into multithreaded applications without | |
319 | customizing the Tcl core. To enable Tcl multithreading support, | |
320 | you must include the \fB--enable-threads\fR option to \fBconfigure\fR | |
321 | when you configure and compile your Tcl core. | |
322 | .PP | |
323 | An important constraint of the Tcl threads implementation is that | |
324 | \fIonly the thread that created a Tcl interpreter can use that | |
325 | interpreter\fR. In other words, multiple threads can not access | |
326 | the same Tcl interpreter. (However, as was the case in previous | |
327 | releases, a single thread can safely create and use multiple | |
328 | interpreters.) | |
329 | .PP | |
330 | .VS 8.3.1 | |
331 | Tcl does provide \fBTcl_CreateThread\fR for creating threads. The | |
332 | caller can determine the size of the stack given to the new thread and | |
333 | modify the behaviour through the supplied \fIflags\fR. The value | |
334 | \fBTCL_THREAD_STACK_DEFAULT\fR for the \fIstackSize\fR indicates that | |
335 | the default size as specified by the operating system is to be used | |
336 | for the new thread. As for the flags, currently are only the values | |
337 | \fBTCL_THREAD_NOFLAGS\fR and \fBTCL_THREAD_JOINABLE\fR defined. The | |
338 | first of them invokes the default behaviour with no | |
339 | specialties. Using the second value marks the new thread as | |
340 | \fIjoinable\fR. This means that another thread can wait for the such | |
341 | marked thread to exit and join it. | |
342 | .PP | |
343 | Restrictions: On some unix systems the pthread-library does not | |
344 | contain the functionality to specify the stacksize of a thread. The | |
345 | specified value for the stacksize is ignored on these systems. Both | |
346 | Windows and Macintosh currently do not support joinable threads. This | |
347 | flag value is therefore ignored on these platforms. | |
348 | .VE | |
349 | .PP | |
350 | Tcl does provide \fBTcl_ExitThread\fR and \fBTcl_FinalizeThread\fR | |
351 | for terminating threads and invoking optional per-thread exit | |
352 | handlers. See the \fBTcl_Exit\fR page for more information on these | |
353 | procedures. | |
354 | .PP | |
355 | .VS | |
356 | The \fBTcl_JoinThread\fR function is provided to allow threads to wait | |
357 | upon the exit of another thread, which must have been marked as | |
358 | joinable through usage of the \fBTCL_THREAD_JOINABLE\fR-flag during | |
359 | its creation via \fBTcl_CreateThread\fR. | |
360 | .PP | |
361 | Trying to wait for the exit of a non-joinable thread or a thread which | |
362 | is already waited upon will result in an error. Waiting for a joinable | |
363 | thread which already exited is possible, the system will retain the | |
364 | necessary information until after the call to \fBTcl_JoinThread\fR. | |
365 | This means that not calling \fBTcl_JoinThread\fR for a joinable thread | |
366 | will cause a memory leak. | |
367 | .VE | |
368 | .PP | |
369 | Tcl provides \fBTcl_ThreadQueueEvent\fR and \fBTcl_ThreadAlert\fR | |
370 | for handling event queueing in multithreaded applications. See | |
371 | the \fBNotifier\fR manual page for more information on these procedures. | |
372 | .PP | |
373 | In this release, the Tcl language itself provides no support for | |
374 | creating multithreaded scripts (for example, scripts that could spawn | |
375 | a Tcl interpreter in a separate thread). If you need to add this | |
376 | feature at this time, see the \fItclThreadTest.c\fR | |
377 | file in the Tcl source distribution for an experimental implementation | |
378 | or use the Tcl "Threading Extension" package implementing thread creation | |
379 | and management commands at the script level. | |
380 | ||
381 | ||
382 | .SH DESCRIPTION | |
383 | A mutex is a lock that is used to serialize all threads through a piece | |
384 | of code by calling \fBTcl_MutexLock\fR and \fBTcl_MutexUnlock\fR. | |
385 | If one thread holds a mutex, any other thread calling \fBTcl_MutexLock\fR will | |
386 | block until \fBTcl_MutexUnlock\fR is called. | |
387 | .VS | |
388 | A mutex can be destroyed after its use by calling \fBTcl_MutexFinalize\fR. | |
389 | The result of locking a mutex twice from the same thread is undefined. | |
390 | On some platforms it will result in a deadlock. | |
391 | .VE | |
392 | The \fBTcl_MutexLock\fR, \fBTcl_MutexUnlock\fR and \fBTcl_MutexFinalize\fR | |
393 | procedures are defined as empty macros if not compiling with threads enabled. | |
394 | For declaration of mutexes the \fBTCL_DECLARE_MUTEX\fR macro should be used. | |
395 | This macro assures correct mutex handling even when the core is compiled | |
396 | without threads enabled. | |
397 | .PP | |
398 | A condition variable is used as a signaling mechanism: | |
399 | a thread can lock a mutex and then wait on a condition variable | |
400 | with \fBTcl_ConditionWait\fR. This atomically releases the mutex lock | |
401 | and blocks the waiting thread until another thread calls | |
402 | \fBTcl_ConditionNotify\fR. The caller of \fBTcl_ConditionNotify\fR should | |
403 | have the associated mutex held by previously calling \fBTcl_MutexLock\fR, | |
404 | but this is not enforced. Notifying the | |
405 | condition variable unblocks all threads waiting on the condition variable, | |
406 | but they do not proceed until the mutex is released with \fBTcl_MutexUnlock\fR. | |
407 | The implementation of \fBTcl_ConditionWait\fR automatically locks | |
408 | the mutex before returning. | |
409 | .PP | |
410 | The caller of \fBTcl_ConditionWait\fR should be prepared for spurious | |
411 | notifications by calling \fBTcl_ConditionWait\fR within a while loop | |
412 | that tests some invariant. | |
413 | .PP | |
414 | .VS | |
415 | A condition variable can be destroyed after its use by calling | |
416 | \fBTcl_ConditionFinalize\fR. | |
417 | .PP | |
418 | The \fBTcl_ConditionNotify\fR, \fBTcl_ConditionWait\fR and | |
419 | \fBTcl_ConditionFinalize\fR procedures are defined as empty macros if | |
420 | not compiling with threads enabled. | |
421 | .VE | |
422 | .PP | |
423 | The \fBTcl_GetThreadData\fR call returns a pointer to a block of | |
424 | thread-private data. Its argument is a key that is shared by all threads | |
425 | and a size for the block of storage. The storage is automatically | |
426 | allocated and initialized to all zeros the first time each thread asks for it. | |
427 | The storage is automatically deallocated by \fBTcl_FinalizeThread\fR. | |
428 | .SH INITIALIZATION | |
429 | .PP | |
430 | All of these synchronization objects are self initializing. | |
431 | They are implemented as opaque pointers that should be NULL | |
432 | upon first use. | |
433 | The mutexes and condition variables are | |
434 | .VS | |
435 | either cleaned up by process exit handlers (if living that long) or | |
436 | explicitly by calls to \fBTcl_MutexFinalize\fR or | |
437 | \fBTcl_ConditionFinalize\fR. | |
438 | .VE | |
439 | Thread local storage is reclaimed during \fBTcl_FinalizeThread\fR. | |
440 | .SH "CREATING THREADS" | |
441 | The API to create threads is not finalized at this time. | |
442 | There are private facilities to create threads that contain a new | |
443 | Tcl interpreter, and to send scripts among threads. | |
444 | Dive into tclThreadTest.c and tclThread.c for examples. | |
445 | .SH "SEE ALSO" | |
446 | Tcl_GetCurrentThread, Tcl_ThreadQueueEvent, Tcl_ThreadAlert, | |
447 | Tcl_ExitThread, Tcl_FinalizeThread, | |
448 | Tcl_CreateThreadExitHandler, Tcl_DeleteThreadExitHandler | |
449 | .SH KEYWORDS | |
450 | thread, mutex, condition variable, thread local storage |