--- /dev/null
+'\"
+'\" Copyright (c) 1999 Scriptics Corporation
+'\" Copyright (c) 1998 Sun Microsystems, Inc.
+'\"
+'\" See the file "license.terms" for information on usage and redistribution
+'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+'\"
+.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_CreateThread, Tcl_JoinThread \- Tcl thread support
+.SH SYNOPSIS
+.nf
+\fB#include <tcl.h>\fR
+.sp
+void
+\fBTcl_ConditionNotify\fR(\fIcondPtr\fR)
+.sp
+void
+\fBTcl_ConditionWait\fR(\fIcondPtr, mutexPtr, timePtr\fR)
+.sp
+void
+\fBTcl_ConditionFinalize\fR(\fIcondPtr\fR)
+.sp
+Void *
+\fBTcl_GetThreadData\fR(\fIkeyPtr, size\fR)
+.sp
+void
+\fBTcl_MutexLock\fR(\fImutexPtr\fR)
+.sp
+void
+\fBTcl_MutexUnlock\fR(\fImutexPtr\fR)
+.sp
+void
+\fBTcl_MutexFinalize\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
+.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 "const Tcl_Time" *timePtr in
+A time limit on the condition wait. NULL to wait forever.
+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
+a different block of storage with this key.
+.AP int *size in
+The size of the thread local storage block. This amount of data
+is allocated and initialized to zero the first time each thread
+calls \fBTcl_GetThreadData\fR.
+.AP Tcl_ThreadId *idPtr out
+The referred storage will contain the id of the newly created thread as
+returned by the operating system.
+.AP Tcl_ThreadId id in
+Id of the thread waited upon.
+.AP Tcl_ThreadCreateProc *proc in
+This procedure will act as the \fBmain()\fR of the newly created
+thread. The specified \fIclientData\fR will be its sole argument.
+.AP ClientData clientData in
+Arbitrary information. Passed as sole argument to the \fIproc\fR.
+.AP int stackSize in
+The size of the stack given to the new thread.
+.AP int flags in
+Bitmask containing flags allowing the caller to modify behavior of
+the new thread.
+.AP int *result out
+The referred storage is used to place the exit code of the thread
+waited upon into it.
+.BE
+.SH INTRODUCTION
+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. Starting with the 8.6 release, Tcl
+multithreading support is on by default. To disable Tcl multithreading
+support, you must include the \fB\-\|\-disable-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, 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 behavior 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 only the values
+\fBTCL_THREAD_NOFLAGS\fR and \fBTCL_THREAD_JOINABLE\fR are defined. The
+first of them invokes the default behavior with no special settings.
+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 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 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
+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
+its creation via \fBTcl_CreateThread\fR.
+.PP
+Trying to wait for the exit of a non-joinable thread or a thread which
+is already waited upon will result in an error. Waiting for a joinable
+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.
+.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 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.
+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 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.
+.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
+and blocks the waiting thread until another thread calls
+\fBTcl_ConditionNotify\fR. The caller of \fBTcl_ConditionNotify\fR should
+have the associated mutex held by previously calling \fBTcl_MutexLock\fR,
+but this is not enforced. Notifying the
+condition variable unblocks all threads waiting on the condition variable,
+but they do not proceed until the mutex is released with \fBTcl_MutexUnlock\fR.
+The implementation of \fBTcl_ConditionWait\fR automatically locks
+the mutex before returning.
+.PP
+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
+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.
+.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_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
+the script level. One such package is the \fBThread\fR package.
+.SH EXAMPLE
+.PP
+To create a thread with portable code, its implementation function should be
+declared as follows:
+.PP
+.CS
+static \fBTcl_ThreadCreateProc\fR MyThreadImplFunc;
+.CE
+.PP
+It should then be defined like this example, which just counts up to a given
+value and then finishes.
+.PP
+.CS
+static \fBTcl_ThreadCreateType\fR
+MyThreadImplFunc(
+ ClientData clientData)
+{
+ int i, limit = (int) clientData;
+ for (i=0 ; i<limit ; i++) {
+ /* doing nothing at all here */
+ }
+ \fBTCL_THREAD_CREATE_RETURN\fR;
+}
+.CE
+.PP
+To create the above thread, make it execute, and wait for it to finish, we
+would do this:
+.PP
+.CS
+int limit = 1000000000;
+ClientData limitData = (void*)((intptr_t) limit);
+Tcl_ThreadId id; \fI/* holds identity of thread created */\fR
+int result;
+
+if (\fBTcl_CreateThread\fR(&id, MyThreadImplFunc, limitData,
+ \fBTCL_THREAD_STACK_DEFAULT\fR,
+ \fBTCL_THREAD_JOINABLE\fR) != TCL_OK) {
+ \fI/* Thread did not create correctly */\fR
+ return;
+}
+\fI/* Do something else for a while here */\fR
+if (\fBTcl_JoinThread\fR(id, &result) != TCL_OK) {
+ \fI/* Thread did not finish properly */\fR
+ return;
+}
+\fI/* All cleaned up nicely */\fR
+.CE
+.SH "SEE ALSO"
+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
OSDN Git Service
