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Diffstat (limited to 'doc/Thread.3')
| -rw-r--r-- | doc/Thread.3 | 92 |
1 files changed, 37 insertions, 55 deletions
diff --git a/doc/Thread.3 b/doc/Thread.3 index 2ffd6ef..80d34ad 100644 --- a/doc/Thread.3 +++ b/doc/Thread.3 @@ -9,7 +9,7 @@ .TH Threads 3 "8.1" Tcl "Tcl Library Procedures" .BS .SH NAME -Tcl_ConditionNotify, Tcl_ConditionWait, Tcl_ConditionFinalize, Tcl_GetThreadData, Tcl_MutexLock, Tcl_MutexUnlock, Tcl_MutexFinalize, Tcl_CreateThread, Tcl_JoinThread \- Tcl thread support. +Tcl_ConditionNotify, Tcl_ConditionWait, Tcl_ConditionFinalize, Tcl_GetThreadData, Tcl_MutexLock, Tcl_MutexUnlock, Tcl_MutexFinalize, Tcl_CreateThread, Tcl_JoinThread \- Tcl thread support .SH SYNOPSIS .nf \fB#include <tcl.h>\fR @@ -41,14 +41,14 @@ int int \fBTcl_JoinThread\fR(\fIid, result\fR) .SH ARGUMENTS -.AS Tcl_ThreadDataKey *keyPtr +.AS Tcl_CreateThreadProc threadProc out .AP Tcl_Condition *condPtr in A condition variable, which must be associated with a mutex lock. .AP Tcl_Mutex *mutexPtr in A mutex lock. .AP Tcl_Time *timePtr in A time limit on the condition wait. NULL to wait forever. -Note that a polling value of 0 seconds doesn't make much sense. +Note that a polling value of 0 seconds does not make much sense. .AP Tcl_ThreadDataKey *keyPtr in This identifies a block of thread local storage. The key should be static and process-wide, yet each thread will end up associating @@ -80,42 +80,38 @@ waited upon into it. Beginning with the 8.1 release, the Tcl core is thread safe, which allows you to incorporate Tcl into multithreaded applications without customizing the Tcl core. To enable Tcl multithreading support, -you must include the \fB--enable-threads\fR option to \fBconfigure\fR +you must include the \fB\-\|\-enable-threads\fR option to \fBconfigure\fR when you configure and compile your Tcl core. .PP An important constraint of the Tcl threads implementation is that \fIonly the thread that created a Tcl interpreter can use that interpreter\fR. In other words, multiple threads can not access -the same Tcl interpreter. (However, as was the case in previous -releases, a single thread can safely create and use multiple -interpreters.) -.PP -.VS 8.3.1 -Tcl does provide \fBTcl_CreateThread\fR for creating threads. The +the same Tcl interpreter. (However, a single thread can safely create +and use multiple interpreters.) +.SH DESCRIPTION +Tcl provides \fBTcl_CreateThread\fR for creating threads. The caller can determine the size of the stack given to the new thread and modify the behaviour through the supplied \fIflags\fR. The value \fBTCL_THREAD_STACK_DEFAULT\fR for the \fIstackSize\fR indicates that the default size as specified by the operating system is to be used -for the new thread. As for the flags, currently are only the values -\fBTCL_THREAD_NOFLAGS\fR and \fBTCL_THREAD_JOINABLE\fR defined. The +for the new thread. As for the flags, currently only the values +\fBTCL_THREAD_NOFLAGS\fR and \fBTCL_THREAD_JOINABLE\fR are defined. The first of them invokes the default behaviour with no specialties. Using the second value marks the new thread as \fIjoinable\fR. This means that another thread can wait for the such marked thread to exit and join it. .PP -Restrictions: On some unix systems the pthread-library does not -contain the functionality to specify the stacksize of a thread. The -specified value for the stacksize is ignored on these systems. Both -Windows and Macintosh currently do not support joinable threads. This -flag value is therefore ignored on these platforms. -.VE +Restrictions: On some UNIX systems the pthread-library does not +contain the functionality to specify the stack size of a thread. The +specified value for the stack size is ignored on these systems. +Windows currently does not support joinable threads. This +flag value is therefore ignored on this platform. .PP -Tcl does provide \fBTcl_ExitThread\fR and \fBTcl_FinalizeThread\fR +Tcl provides the \fBTcl_ExitThread\fR and \fBTcl_FinalizeThread\fR functions for terminating threads and invoking optional per-thread exit handlers. See the \fBTcl_Exit\fR page for more information on these procedures. .PP -.VS The \fBTcl_JoinThread\fR function is provided to allow threads to wait upon the exit of another thread, which must have been marked as joinable through usage of the \fBTCL_THREAD_JOINABLE\fR-flag during @@ -127,36 +123,29 @@ thread which already exited is possible, the system will retain the necessary information until after the call to \fBTcl_JoinThread\fR. This means that not calling \fBTcl_JoinThread\fR for a joinable thread will cause a memory leak. -.VE .PP +The \fBTcl_GetThreadData\fR call returns a pointer to a block of +thread-private data. Its argument is a key that is shared by all threads +and a size for the block of storage. The storage is automatically +allocated and initialized to all zeros the first time each thread asks for it. +The storage is automatically deallocated by \fBTcl_FinalizeThread\fR. +.SS "SYNCHRONIZATION AND COMMUNICATION" Tcl provides \fBTcl_ThreadQueueEvent\fR and \fBTcl_ThreadAlert\fR -for handling event queueing in multithreaded applications. See +for handling event queuing in multithreaded applications. See the \fBNotifier\fR manual page for more information on these procedures. .PP -In this release, the Tcl language itself provides no support for -creating multithreaded scripts (for example, scripts that could spawn -a Tcl interpreter in a separate thread). If you need to add this -feature at this time, see the \fItclThreadTest.c\fR -file in the Tcl source distribution for an experimental implementation -or use the Tcl "Threading Extension" package implementing thread creation -and management commands at the script level. - - -.SH DESCRIPTION A mutex is a lock that is used to serialize all threads through a piece of code by calling \fBTcl_MutexLock\fR and \fBTcl_MutexUnlock\fR. If one thread holds a mutex, any other thread calling \fBTcl_MutexLock\fR will block until \fBTcl_MutexUnlock\fR is called. -.VS A mutex can be destroyed after its use by calling \fBTcl_MutexFinalize\fR. The result of locking a mutex twice from the same thread is undefined. On some platforms it will result in a deadlock. -.VE The \fBTcl_MutexLock\fR, \fBTcl_MutexUnlock\fR and \fBTcl_MutexFinalize\fR procedures are defined as empty macros if not compiling with threads enabled. For declaration of mutexes the \fBTCL_DECLARE_MUTEX\fR macro should be used. This macro assures correct mutex handling even when the core is compiled -without threads enabled. +without threads enabled. .PP A condition variable is used as a signaling mechanism: a thread can lock a mutex and then wait on a condition variable @@ -174,40 +163,33 @@ The caller of \fBTcl_ConditionWait\fR should be prepared for spurious notifications by calling \fBTcl_ConditionWait\fR within a while loop that tests some invariant. .PP -.VS A condition variable can be destroyed after its use by calling \fBTcl_ConditionFinalize\fR. .PP The \fBTcl_ConditionNotify\fR, \fBTcl_ConditionWait\fR and \fBTcl_ConditionFinalize\fR procedures are defined as empty macros if not compiling with threads enabled. -.VE -.PP -The \fBTcl_GetThreadData\fR call returns a pointer to a block of -thread-private data. Its argument is a key that is shared by all threads -and a size for the block of storage. The storage is automatically -allocated and initialized to all zeros the first time each thread asks for it. -The storage is automatically deallocated by \fBTcl_FinalizeThread\fR. -.SH INITIALIZATION +.SS INITIALIZATION .PP -All of these synchronization objects are self initializing. +All of these synchronization objects are self-initializing. They are implemented as opaque pointers that should be NULL upon first use. The mutexes and condition variables are -.VS either cleaned up by process exit handlers (if living that long) or explicitly by calls to \fBTcl_MutexFinalize\fR or \fBTcl_ConditionFinalize\fR. -.VE Thread local storage is reclaimed during \fBTcl_FinalizeThread\fR. -.SH "CREATING THREADS" -The API to create threads is not finalized at this time. -There are private facilities to create threads that contain a new -Tcl interpreter, and to send scripts among threads. -Dive into tclThreadTest.c and tclThread.c for examples. +.SH "SCRIPT-LEVEL ACCESS TO THREADS" +.VS 8.5 +Tcl provides no built-in commands for scripts to use to create, +manage, or join threads, nor any script-level access to mutex or +condition variables. It provides such facilities only via C +interfaces, and leaves it up to packages to expose these matters to +the script level. One such package is the \fBThread\fR package. +.VE 8.5 .SH "SEE ALSO" -Tcl_GetCurrentThread, Tcl_ThreadQueueEvent, Tcl_ThreadAlert, -Tcl_ExitThread, Tcl_FinalizeThread, -Tcl_CreateThreadExitHandler, Tcl_DeleteThreadExitHandler +Tcl_GetCurrentThread(3), Tcl_ThreadQueueEvent(3), Tcl_ThreadAlert(3), +Tcl_ExitThread(3), Tcl_FinalizeThread(3), Tcl_CreateThreadExitHandler(3), +Tcl_DeleteThreadExitHandler(3), Thread .SH KEYWORDS thread, mutex, condition variable, thread local storage |