Tcl Source Code

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'\" Copyright (c) 1999 Scriptics Corporation
'\" Copyright (c) 1998 Sun Microsystems, Inc.
'\"
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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.TH Threads 3 "8.1" Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_ConditionNotify, Tcl_ConditionWait, Tcl_ConditionFinalize, Tcl_GetThreadData, Tcl_MutexLock, Tcl_MutexUnlock, Tcl_MutexFinalize, Tcl_MutexUnlockAndFinalize, Tcl_CreateThread, Tcl_JoinThread \- Tcl thread support
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
void
\fBTcl_ConditionNotify\fR(\fIcondPtr\fR)
.sp

.sp
void
\fBTcl_MutexUnlock\fR(\fImutexPtr\fR)
.sp
void
\fBTcl_MutexFinalize\fR(\fImutexPtr\fR)
.sp
void
\fBTcl_MutexUnlockAndFinalize\fR(\fImutexPtr\fR)
.sp
int
\fBTcl_CreateThread\fR(\fIidPtr, proc, clientData, stackSize, flags\fR)
.sp
int
\fBTcl_JoinThread\fR(\fIid, result\fR)
.SH ARGUMENTS
.AS Tcl_CreateThreadProc proc out

for handling event queuing in multithreaded applications.  See
the \fBNotifier\fR manual page for more information on these procedures.
.PP
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.
A mutex can be destroyed after its use by calling \fBTcl_MutexFinalize\fR or
\fBTcl_MutexUnlockAndFinalize\fR.  It is illegal to destroy a locked mutex
with \fBTcl_MutexFinalize\fR; however, it is legal to destroy a locked mutex
with \fBTcl_MutexUnlockAndFinalize\fR.
The result of locking a mutex twice from the same thread is undefined.
On some platforms it will result in a deadlock.
The \fBTcl_MutexLock\fR, \fBTcl_MutexUnlock\fR, \fBTcl_MutexFinalize\fR, and
\fBTcl_MutexUnlockAndFinalize\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.
.PP
A condition variable is used as a signaling mechanism:
a thread can lock a mutex and then wait on a condition variable
with \fBTcl_ConditionWait\fR.  This atomically releases the mutex lock

.SS INITIALIZATION
.PP
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
either cleaned up by process exit handlers (if living that long) or
explicitly by calls to \fBTcl_MutexFinalize\fR (or
\fBTcl_MutexUnlockAndFinalize\fR) and \fBTcl_ConditionFinalize\fR.
Thread local storage is reclaimed during \fBTcl_FinalizeThread\fR.
.SH "SCRIPT-LEVEL ACCESS TO THREADS"
.PP
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