Move the obsolete README.threads out of sight to ext/Threads;

save one part of the IRIX knowledge in INSTALL (though IRIX
6.2 is quite old...)

p4raw-id: //depot/perl@16995

1 files changed, 349 insertions, 0 deletions

diff --git a/ext/Thread/README.threads b/ext/Thread/README.threads
new file mode 100644
index 0000000000..9cd0dbcb20
--- /dev/null
+++ b/ext/Thread/README.threads
@@ -0,0 +1,349 @@
+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