| 1 | '\" |
| 2 | '\" Copyright (c) 1999 Scriptics Corporation |
| 3 | '\" Copyright (c) 1998 Sun Microsystems, Inc. |
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| 9 | '\" |
| 10 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
| 11 | '\" manual entries. |
| 12 | '\" |
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| 60 | '\" End of list of standard options for a Tk widget. |
| 61 | '\" |
| 62 | '\" .OP cmdName dbName dbClass |
| 63 | '\" Start of description of a specific option. cmdName gives the |
| 64 | '\" option's name as specified in the class command, dbName gives |
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| 71 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ |
| 72 | '\" |
| 73 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
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| 206 | '\" # SO - start of list of standard options |
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| 208 | .SH "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 |
| 227 | Database Name: \\fB\\$2\\fR |
| 228 | Database Class: \\fB\\$3\\fR |
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| 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 |