and the 'Thread' module offers an interface to both 5005threads and
ithreads (whichever has been configured).
+For IRIX 6.2, you have to have the following patches installed:
+
+ 1404 Irix 6.2 Posix 1003.1b man pages
+ 1645 IRIX 6.2 & 6.3 POSIX header file updates
+ 2000 Irix 6.2 Posix 1003.1b support modules
+ 2254 Pthread library fixes
+ 2401 6.2 all platform kernel rollup
+
+IMPORTANT: Without patch 2401, a kernel bug in IRIX 6.2 will cause
+your machine to panic and crash when running threaded perl. IRIX 6.3
+and later are okay.
+
=head2 Large file support.
Since Perl 5.6.0, Perl has supported large files (files larger than
ext/Thread/Notes Thread notes
ext/Thread/queue.tx Test Thread::Queue module
ext/Thread/README Thread README
+ext/Thread/README.threads Notes about multithreading
ext/Thread/specific.tx Test thread-specific user data
ext/Thread/sync.tx Test thread synchronisation
ext/Thread/sync2.tx Test thread synchronisation
README.plan9 Notes about Plan9 port
README.qnx Notes about QNX port
README.solaris Notes about Solaris port
-README.threads Notes about multithreading
README.tru64 Notes about Tru64
README.tw About using Perl and Traditional Chinese
README.uts Notes about UTS
+++ /dev/null
-NOTE: This documentation describes the style of threading that was
-available in Perl 5.005. Perl 5.6.0 introduced the early beginnings of
-interpreter-based threads support, also known as ithreads, and in Perl
-5.8.0 the interpeter threads became available from perl level through
-the threads and threads::shared modules (in Perl 5.6 ithreads are
-available only internally and to XS extension builders, and used
-by the Win32 port for emulating fork()). As of Perl 5.8.0, ithreads has
-become the standard threading model for Perl.
-
-If you really want the older support for threads described below,
-it is enabled with:
-
- sh Configure -Dusethreads -Duse5005threads
-
-Be warned that the old 5.005 implementation of threads is known
-to be quite buggy, and unmaintained, which means that the bugs
-are there to stay. (We are not mean by not fixing the bugs:
-the bugs are just really, really, really hard to fix. Honest.)
-
-The rest of this document only applies to the use5005threads style of
-threads, and the comments on what works on which platform are highly
-obsolete and preserved here for archaeology buffs only. The
-architecture specific hints files do all the necessary option
-tweaking automatically during Configure, both for the 5.005 threads
-and for the new interpreter threads.
-
----------------------------------------------------------------------------
-
-Support for threading is still in the highly experimental stages. There
-are known race conditions that show up under high contention on SMP
-machines. Internal implementation is still subject to changes.
-It is not recommended for production use at this time.
-
----------------------------------------------------------------------------
-
-Building
-
-If your system is in the following list you should be able to just:
-
- ./Configure -Dusethreads -Duse5005threads -des
- make
-
-and ignore the rest of this "Building" section. If not, continue
-from the "Problems" section.
-
- * Linux 2.* (with the LinuxThreads library installed:
- that's the linuxthreads and linuxthreads-devel RPMs
- for RedHat)
-
- * Tru64 UNIX (formerly Digital UNIX formerly DEC OSF/1)
- (see additional note below)
-
- * Solaris 2.* for recentish x (2.5 is OK)
-
- * IRIX 6.2 or newer. 6.2 will require a few OS patches.
- IMPORTANT: Without patch 2401 (or its replacement),
- a kernel bug in IRIX 6.2 will cause your machine to
- panic and crash when running threaded perl.
- IRIX 6.3 and up should be OK. See lower down for patch details.
-
- * AIX 4.1.5 or newer.
-
- * FreeBSD 2.2.8 or newer.
-
- * OpenBSD
-
- * NeXTstep, OpenStep
-
- * OS/2
-
- * DOS DJGPP
-
- * VM/ESA
-
----------------------------------------------------------------------------
-
-Problems
-
-If the simple way doesn't work or you are using another platform which
-you believe supports POSIX.1c threads then read on. Additional
-information may be in a platform-specific "hints" file in the hints/
-subdirectory.
-
-On platforms that use Configure to build perl, omit the -d from your
-./Configure arguments. For example, use:
-
- ./Configure -Dusethreads -Duse5005threads
-
-When Configure prompts you for ccflags, insert any other arguments in
-there that your compiler needs to use POSIX threads (-D_REENTRANT,
--pthreads, -threads, -pthread, -thread, are good guesses). When
-Configure prompts you for linking flags, include any flags required
-for threading (usually nothing special is required here). Finally,
-when Configure prompts you for libraries, include any necessary
-libraries (e.g. -lpthread). Pay attention to the order of libraries.
-It is probably necessary to specify your threading library *before*
-your standard C library, e.g. it might be necessary to have -lpthread
--lc, instead of -lc -lpthread. You may also need to use -lc_r instead
-of -lc.
-
-Once you have specified all your compiler flags, you can have Configure
-accept all the defaults for the remainder of the session by typing &-d
-at any Configure prompt.
-
-Some additional notes (some of these may be obsolete now, other items
-may be handled automatically):
-
-For Digital Unix 4.x:
- Add -pthread to ccflags
- Add -pthread to ldflags
- Add -lpthread -lc_r to lddlflags
-
- For some reason, the extra includes for pthreads make Digital UNIX
- complain fatally about the sbrk() declaration in perl's malloc.c
- so use the native malloc, e.g. sh Configure -Uusemymalloc, or
- manually edit your config.sh as follows:
- Change usemymalloc to n
- Zap mallocobj and mallocsrc (foo='')
- Change d_mymalloc to undef
-
-For Digital Unix 3.x (Formerly DEC OSF/1):
- Add -DOLD_PTHREADS_API to ccflags
- If compiling with the GNU cc compiler, remove -threads from ccflags
-
- (The following should be done automatically if you call Configure
- with the -Dusethreads option).
- Add -lpthread -lmach -lc_r to libs (in the order specified).
-
-For IRIX:
- (This should all be done automatically by the hint file).
- Add -lpthread to libs
- For IRIX 6.2, you have to have the following patches installed:
- 1404 Irix 6.2 Posix 1003.1b man pages
- 1645 IRIX 6.2 & 6.3 POSIX header file updates
- 2000 Irix 6.2 Posix 1003.1b support modules
- 2254 Pthread library fixes
- 2401 6.2 all platform kernel rollup
- IMPORTANT: Without patch 2401, a kernel bug in IRIX 6.2 will
- cause your machine to panic and crash when running threaded perl.
- IRIX 6.3 and up should be OK.
-
- For IRIX 6.3 and 6.4 the pthreads should work out of the box.
- Thanks to Hannu Napari <Hannu.Napari@hut.fi> for the IRIX
- pthreads patches information.
-
-For AIX:
- (This should all be done automatically by the hint file).
- Change cc to xlc_r or cc_r.
- Add -DNEED_PTHREAD_INIT to ccflags and cppflags
- Add -lc_r to libswanted
- Change -lc in lddflags to be -lpthread -lc_r -lc
-
-For Win32:
- See README.win32, and the notes at the beginning of win32/Makefile
- or win32/makefile.mk.
-
-Now you can do a
- make
-
-When you succeed in compiling and testing ("make test" after your
-build) a threaded Perl in a platform previously unknown to support
-threaded perl, please let perlbug@perl.com know about your victory.
-Explain what you did in painful detail.
-
----------------------------------------------------------------------------
-
-O/S specific bugs
-
-Irix 6.2: See the Irix warning above.
-
-LinuxThreads 0.5 has a bug which can cause file descriptor 0 to be
-closed after a fork() leading to many strange symptoms. Version 0.6
-has this fixed but the following patch can be applied to 0.5 for now:
-
------------------------------ cut here -----------------------------
---- linuxthreads-0.5/pthread.c.ORI Mon Oct 6 13:55:50 1997
-+++ linuxthreads-0.5/pthread.c Mon Oct 6 13:57:24 1997
-@@ -312,8 +312,10 @@
- free(pthread_manager_thread_bos);
- pthread_manager_thread_bos = pthread_manager_thread_tos = NULL;
- /* Close the two ends of the pipe */
-- close(pthread_manager_request);
-- close(pthread_manager_reader);
-+ if (pthread_manager_request >= 0) {
-+ close(pthread_manager_request);
-+ close(pthread_manager_reader);
-+ }
- pthread_manager_request = pthread_manager_reader = -1;
- /* Update the pid of the main thread */
- self->p_pid = getpid();
------------------------------ cut here -----------------------------
-
-
-Building the Thread extension
-
-The Thread extension is now part of the main perl distribution tree.
-If you did Configure -Dusethreads -Duse5005threads then it will have been
-added to the list of extensions automatically.
-
-You can try some of the tests with
- cd ext/Thread
- perl create.t
- perl join.t
- perl lock.t
- perl io.t
-etc.
-The io one leaves a thread reading from the keyboard on stdin so
-as the ping messages appear you can type lines and see them echoed.
-
-Try running the main perl test suite too. There are known
-failures for some of the DBM/DB extensions (if their underlying
-libraries were not compiled to be thread-aware).
-
----------------------------------------------------------------------------
-
-Bugs
-
-* FAKE_THREADS should produce a working perl but the Thread
-extension won't build with it yet. (FAKE_THREADS has not been
-tested at all in recent times.)
-
-* There may still be races where bugs show up under contention.
-
----------------------------------------------------------------------------
-
-Debugging
-
-Use the -DS command-line option to turn on debugging of the
-multi-threading code. Under Linux, that also turns on a quick
-hack I did to grab a bit of extra information from segfaults.
-If you have a fancier gdb/threads setup than I do then you'll
-have to delete the lines in perl.c which say
- #if defined(DEBUGGING) && defined(USE_5005THREADS) && defined(__linux__)
- DEBUG_S(signal(SIGSEGV, (void(*)(int))catch_sigsegv););
- #endif
-
----------------------------------------------------------------------------
-
-Background
-
-Some old globals (e.g. stack_sp, op) and some old per-interpreter
-variables (e.g. tmps_stack, cxstack) move into struct thread.
-All fields of struct thread which derived from original perl
-variables have names of the form Tfoo. For example, stack_sp becomes
-the field Tstack_sp of struct thread. For those fields which moved
-from original perl, thread.h does
- #define foo (thr->Tfoo)
-This means that all functions in perl which need to use one of these
-fields need an (automatic) variable thr which points at the current
-thread's struct thread. For pp_foo functions, it is passed around as
-an argument, for other functions they do
- dTHR;
-which declares and initialises thr from thread-specific data
-via pthread_getspecific. If a function fails to compile with an
-error about "no such variable thr", it probably just needs a dTHR
-at the top.
-
-
-Fake threads
-
-For FAKE_THREADS, thr is a global variable and perl schedules threads
-by altering thr in between appropriate ops. The next and prev fields
-of struct thread keep all fake threads on a doubly linked list and
-the next_run and prev_run fields keep all runnable threads on a
-doubly linked list. Mutexes are stubs for FAKE_THREADS. Condition
-variables are implemented as a list of waiting threads.
-
-
-Mutexes and condition variables
-
-The API is via macros MUTEX_{INIT,LOCK,UNLOCK,DESTROY} and
-COND_{INIT,WAIT,SIGNAL,BROADCAST,DESTROY}.
-
-A mutex is only required to be a simple, fast mutex (e.g. it does not
-have to be recursive). It is only ever held across very short pieces
-of code. Condition variables are only ever signalled/broadcast while
-their associated mutex is held. (This constraint simplifies the
-implementation of condition variables in certain porting situations.)
-For POSIX threads, perl mutexes and condition variables correspond to
-POSIX ones. For FAKE_THREADS, mutexes are stubs and condition variables
-are implemented as lists of waiting threads. For FAKE_THREADS, a thread
-waits on a condition variable by removing itself from the runnable
-list, calling SCHEDULE to change thr to the next appropriate
-runnable thread and returning op (i.e. the new threads next op).
-This means that fake threads can only block while in PP code.
-A PP function which contains a COND_WAIT must be prepared to
-handle such restarts and can use the field "private" of struct
-thread to record its state. For fake threads, COND_SIGNAL and
-COND_BROADCAST work by putting back all the threads on the
-condition variables list into the run queue. Note that a mutex
-must *not* be held while returning from a PP function.
-
-Perl locks and condition variables are both implemented as a
-condpair_t structure, containing a mutex, an "owner" condition
-variable, an owner thread field and another condition variable).
-The structure is attached by 'm' magic to any SV. pp_lock locks
-such an object by waiting on the ownercond condition variable until
-the owner field is zero and then setting the owner field to its own
-thread pointer. The lock is semantically recursive so if the owner
-field already matches the current thread then pp_lock returns
-straight away. If the owner field has to be filled in then
-unlock_condpair is queued as an end-of-block destructor and
-that function zeroes out the owner field and signals the ownercond
-condition variable, thus waking up any other thread that wants to
-lock it. When used as a condition variable, the condpair is locked
-(involving the above wait-for-ownership and setting the owner field)
-and the spare condition variable field is used for waiting on.
-
-
-Thread states
-
-
- $t->join
-R_JOINABLE ---------------------> R_JOINED >----\
- | \ pthread_join(t) | ^ |
- | \ | | join | pthread_join
- | \ | | |
- | \ | \------/
- | \ |
- | \ |
- | $t->detach\ pthread_detach |
- | _\| |
-ends| R_DETACHED ends | unlink
- | \ |
- | ends \ unlink |
- | \ |
- | \ |
- | \ |
- | \ |
- | \ |
- V join detach _\| V
-ZOMBIE ----------------------------> DEAD
- pthread_join pthread_detach
- and unlink and unlink
-
-
-
-Malcolm Beattie
-mbeattie@sable.ox.ac.uk
-Last updated: 27 November 1997
-
-Configure-related info updated 16 July 1998 by
-Andy Dougherty <doughera@lafayette.edu>
-
-Other minor updates 10 Feb 1999 by
-Gurusamy Sarathy
-
-More platforms added 26 Jul 1999 by
-Jarkko Hietaniemi
--- /dev/null
+NOTE: This documentation describes the style of threading that was
+available in Perl 5.005. Perl 5.6.0 introduced the early beginnings of
+interpreter-based threads support, also known as ithreads, and in Perl
+5.8.0 the interpeter threads became available from perl level through
+the threads and threads::shared modules (in Perl 5.6 ithreads are
+available only internally and to XS extension builders, and used
+by the Win32 port for emulating fork()). As of Perl 5.8.0, ithreads has
+become the standard threading model for Perl.
+
+If you really want the older support for threads described below,
+it is enabled with:
+
+ sh Configure -Dusethreads -Duse5005threads
+
+Be warned that the old 5.005 implementation of threads is known
+to be quite buggy, and unmaintained, which means that the bugs
+are there to stay. (We are not mean by not fixing the bugs:
+the bugs are just really, really, really hard to fix. Honest.)
+
+The rest of this document only applies to the use5005threads style of
+threads, and the comments on what works on which platform are highly
+obsolete and preserved here for archaeology buffs only. The
+architecture specific hints files do all the necessary option
+tweaking automatically during Configure, both for the 5.005 threads
+and for the new interpreter threads.
+
+---------------------------------------------------------------------------
+
+Support for threading is still in the highly experimental stages. There
+are known race conditions that show up under high contention on SMP
+machines. Internal implementation is still subject to changes.
+It is not recommended for production use at this time.
+
+---------------------------------------------------------------------------
+
+Building
+
+If your system is in the following list you should be able to just:
+
+ ./Configure -Dusethreads -Duse5005threads -des
+ make
+
+and ignore the rest of this "Building" section. If not, continue
+from the "Problems" section.
+
+ * Linux 2.* (with the LinuxThreads library installed:
+ that's the linuxthreads and linuxthreads-devel RPMs
+ for RedHat)
+
+ * Tru64 UNIX (formerly Digital UNIX formerly DEC OSF/1)
+ (see additional note below)
+
+ * Solaris 2.* for recentish x (2.5 is OK)
+
+ * IRIX 6.2 or newer. 6.2 will require a few OS patches.
+ IMPORTANT: Without patch 2401 (or its replacement),
+ a kernel bug in IRIX 6.2 will cause your machine to
+ panic and crash when running threaded perl.
+ IRIX 6.3 and up should be OK. See lower down for patch details.
+
+ * AIX 4.1.5 or newer.
+
+ * FreeBSD 2.2.8 or newer.
+
+ * OpenBSD
+
+ * NeXTstep, OpenStep
+
+ * OS/2
+
+ * DOS DJGPP
+
+ * VM/ESA
+
+---------------------------------------------------------------------------
+
+Problems
+
+If the simple way doesn't work or you are using another platform which
+you believe supports POSIX.1c threads then read on. Additional
+information may be in a platform-specific "hints" file in the hints/
+subdirectory.
+
+On platforms that use Configure to build perl, omit the -d from your
+./Configure arguments. For example, use:
+
+ ./Configure -Dusethreads -Duse5005threads
+
+When Configure prompts you for ccflags, insert any other arguments in
+there that your compiler needs to use POSIX threads (-D_REENTRANT,
+-pthreads, -threads, -pthread, -thread, are good guesses). When
+Configure prompts you for linking flags, include any flags required
+for threading (usually nothing special is required here). Finally,
+when Configure prompts you for libraries, include any necessary
+libraries (e.g. -lpthread). Pay attention to the order of libraries.
+It is probably necessary to specify your threading library *before*
+your standard C library, e.g. it might be necessary to have -lpthread
+-lc, instead of -lc -lpthread. You may also need to use -lc_r instead
+of -lc.
+
+Once you have specified all your compiler flags, you can have Configure
+accept all the defaults for the remainder of the session by typing &-d
+at any Configure prompt.
+
+Some additional notes (some of these may be obsolete now, other items
+may be handled automatically):
+
+For Digital Unix 4.x:
+ Add -pthread to ccflags
+ Add -pthread to ldflags
+ Add -lpthread -lc_r to lddlflags
+
+ For some reason, the extra includes for pthreads make Digital UNIX
+ complain fatally about the sbrk() declaration in perl's malloc.c
+ so use the native malloc, e.g. sh Configure -Uusemymalloc, or
+ manually edit your config.sh as follows:
+ Change usemymalloc to n
+ Zap mallocobj and mallocsrc (foo='')
+ Change d_mymalloc to undef
+
+For Digital Unix 3.x (Formerly DEC OSF/1):
+ Add -DOLD_PTHREADS_API to ccflags
+ If compiling with the GNU cc compiler, remove -threads from ccflags
+
+ (The following should be done automatically if you call Configure
+ with the -Dusethreads option).
+ Add -lpthread -lmach -lc_r to libs (in the order specified).
+
+For IRIX:
+ (This should all be done automatically by the hint file).
+ Add -lpthread to libs
+ For IRIX 6.2, you have to have the following patches installed:
+ 1404 Irix 6.2 Posix 1003.1b man pages
+ 1645 IRIX 6.2 & 6.3 POSIX header file updates
+ 2000 Irix 6.2 Posix 1003.1b support modules
+ 2254 Pthread library fixes
+ 2401 6.2 all platform kernel rollup
+ IMPORTANT: Without patch 2401, a kernel bug in IRIX 6.2 will
+ cause your machine to panic and crash when running threaded perl.
+ IRIX 6.3 and up should be OK.
+
+ For IRIX 6.3 and 6.4 the pthreads should work out of the box.
+ Thanks to Hannu Napari <Hannu.Napari@hut.fi> for the IRIX
+ pthreads patches information.
+
+For AIX:
+ (This should all be done automatically by the hint file).
+ Change cc to xlc_r or cc_r.
+ Add -DNEED_PTHREAD_INIT to ccflags and cppflags
+ Add -lc_r to libswanted
+ Change -lc in lddflags to be -lpthread -lc_r -lc
+
+For Win32:
+ See README.win32, and the notes at the beginning of win32/Makefile
+ or win32/makefile.mk.
+
+Now you can do a
+ make
+
+When you succeed in compiling and testing ("make test" after your
+build) a threaded Perl in a platform previously unknown to support
+threaded perl, please let perlbug@perl.com know about your victory.
+Explain what you did in painful detail.
+
+---------------------------------------------------------------------------
+
+O/S specific bugs
+
+Irix 6.2: See the Irix warning above.
+
+LinuxThreads 0.5 has a bug which can cause file descriptor 0 to be
+closed after a fork() leading to many strange symptoms. Version 0.6
+has this fixed but the following patch can be applied to 0.5 for now:
+
+----------------------------- cut here -----------------------------
+--- linuxthreads-0.5/pthread.c.ORI Mon Oct 6 13:55:50 1997
++++ linuxthreads-0.5/pthread.c Mon Oct 6 13:57:24 1997
+@@ -312,8 +312,10 @@
+ free(pthread_manager_thread_bos);
+ pthread_manager_thread_bos = pthread_manager_thread_tos = NULL;
+ /* Close the two ends of the pipe */
+- close(pthread_manager_request);
+- close(pthread_manager_reader);
++ if (pthread_manager_request >= 0) {
++ close(pthread_manager_request);
++ close(pthread_manager_reader);
++ }
+ pthread_manager_request = pthread_manager_reader = -1;
+ /* Update the pid of the main thread */
+ self->p_pid = getpid();
+----------------------------- cut here -----------------------------
+
+
+Building the Thread extension
+
+The Thread extension is now part of the main perl distribution tree.
+If you did Configure -Dusethreads -Duse5005threads then it will have been
+added to the list of extensions automatically.
+
+You can try some of the tests with
+ cd ext/Thread
+ perl create.t
+ perl join.t
+ perl lock.t
+ perl io.t
+etc.
+The io one leaves a thread reading from the keyboard on stdin so
+as the ping messages appear you can type lines and see them echoed.
+
+Try running the main perl test suite too. There are known
+failures for some of the DBM/DB extensions (if their underlying
+libraries were not compiled to be thread-aware).
+
+---------------------------------------------------------------------------
+
+Bugs
+
+* FAKE_THREADS should produce a working perl but the Thread
+extension won't build with it yet. (FAKE_THREADS has not been
+tested at all in recent times.)
+
+* There may still be races where bugs show up under contention.
+
+---------------------------------------------------------------------------
+
+Debugging
+
+Use the -DS command-line option to turn on debugging of the
+multi-threading code. Under Linux, that also turns on a quick
+hack I did to grab a bit of extra information from segfaults.
+If you have a fancier gdb/threads setup than I do then you'll
+have to delete the lines in perl.c which say
+ #if defined(DEBUGGING) && defined(USE_5005THREADS) && defined(__linux__)
+ DEBUG_S(signal(SIGSEGV, (void(*)(int))catch_sigsegv););
+ #endif
+
+---------------------------------------------------------------------------
+
+Background
+
+Some old globals (e.g. stack_sp, op) and some old per-interpreter
+variables (e.g. tmps_stack, cxstack) move into struct thread.
+All fields of struct thread which derived from original perl
+variables have names of the form Tfoo. For example, stack_sp becomes
+the field Tstack_sp of struct thread. For those fields which moved
+from original perl, thread.h does
+ #define foo (thr->Tfoo)
+This means that all functions in perl which need to use one of these
+fields need an (automatic) variable thr which points at the current
+thread's struct thread. For pp_foo functions, it is passed around as
+an argument, for other functions they do
+ dTHR;
+which declares and initialises thr from thread-specific data
+via pthread_getspecific. If a function fails to compile with an
+error about "no such variable thr", it probably just needs a dTHR
+at the top.
+
+
+Fake threads
+
+For FAKE_THREADS, thr is a global variable and perl schedules threads
+by altering thr in between appropriate ops. The next and prev fields
+of struct thread keep all fake threads on a doubly linked list and
+the next_run and prev_run fields keep all runnable threads on a
+doubly linked list. Mutexes are stubs for FAKE_THREADS. Condition
+variables are implemented as a list of waiting threads.
+
+
+Mutexes and condition variables
+
+The API is via macros MUTEX_{INIT,LOCK,UNLOCK,DESTROY} and
+COND_{INIT,WAIT,SIGNAL,BROADCAST,DESTROY}.
+
+A mutex is only required to be a simple, fast mutex (e.g. it does not
+have to be recursive). It is only ever held across very short pieces
+of code. Condition variables are only ever signalled/broadcast while
+their associated mutex is held. (This constraint simplifies the
+implementation of condition variables in certain porting situations.)
+For POSIX threads, perl mutexes and condition variables correspond to
+POSIX ones. For FAKE_THREADS, mutexes are stubs and condition variables
+are implemented as lists of waiting threads. For FAKE_THREADS, a thread
+waits on a condition variable by removing itself from the runnable
+list, calling SCHEDULE to change thr to the next appropriate
+runnable thread and returning op (i.e. the new threads next op).
+This means that fake threads can only block while in PP code.
+A PP function which contains a COND_WAIT must be prepared to
+handle such restarts and can use the field "private" of struct
+thread to record its state. For fake threads, COND_SIGNAL and
+COND_BROADCAST work by putting back all the threads on the
+condition variables list into the run queue. Note that a mutex
+must *not* be held while returning from a PP function.
+
+Perl locks and condition variables are both implemented as a
+condpair_t structure, containing a mutex, an "owner" condition
+variable, an owner thread field and another condition variable).
+The structure is attached by 'm' magic to any SV. pp_lock locks
+such an object by waiting on the ownercond condition variable until
+the owner field is zero and then setting the owner field to its own
+thread pointer. The lock is semantically recursive so if the owner
+field already matches the current thread then pp_lock returns
+straight away. If the owner field has to be filled in then
+unlock_condpair is queued as an end-of-block destructor and
+that function zeroes out the owner field and signals the ownercond
+condition variable, thus waking up any other thread that wants to
+lock it. When used as a condition variable, the condpair is locked
+(involving the above wait-for-ownership and setting the owner field)
+and the spare condition variable field is used for waiting on.
+
+
+Thread states
+
+
+ $t->join
+R_JOINABLE ---------------------> R_JOINED >----\
+ | \ pthread_join(t) | ^ |
+ | \ | | join | pthread_join
+ | \ | | |
+ | \ | \------/
+ | \ |
+ | \ |
+ | $t->detach\ pthread_detach |
+ | _\| |
+ends| R_DETACHED ends | unlink
+ | \ |
+ | ends \ unlink |
+ | \ |
+ | \ |
+ | \ |
+ | \ |
+ | \ |
+ V join detach _\| V
+ZOMBIE ----------------------------> DEAD
+ pthread_join pthread_detach
+ and unlink and unlink
+
+
+
+Malcolm Beattie
+mbeattie@sable.ox.ac.uk
+Last updated: 27 November 1997
+
+Configure-related info updated 16 July 1998 by
+Andy Dougherty <doughera@lafayette.edu>
+
+Other minor updates 10 Feb 1999 by
+Gurusamy Sarathy
+
+More platforms added 26 Jul 1999 by
+Jarkko Hietaniemi
projects / platform / upstream / perl.git / commitdiff