+NOTE: This documentation describes the style of threading that was
+available in 5.005. Perl v5.6 also has the early beginnings of
+interpreter-based threads support (which is what will be enabled by
+default when you simply ask for -Dusethreads). However, be advised
+that interpreter threads cannot as yet be created from the Perl level
+yet. If you're looking to create threads from within Perl, chances
+are you _don't_ want interpreter threads, but want the older support
+for threads described below, enabled with:
+
+ sh Configure -Dusethreads -Duse5005threads
+
+The rest of this document only applies to the use5005threads style of
+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() delcaration 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 previosuly 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_THREADS) && 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 (apart from a few only applicable to
-FAKE_THREADS) are of the form Tfoo. For example, stack_sp becomes
+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)
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
Mutexes and condition variables
The API is via macros MUTEX_{INIT,LOCK,UNLOCK,DESTROY} and
-COND_{INIT,WAIT,SIGNAL,BROADCAST,DESTROY}. For POSIX threads,
-perl mutexes and condition variables correspond to POSIX ones.
-For FAKE_THREADS, mutexes are stubs and condition variables are
-implmented as lists of waiting threads. For FAKE_THREADS, a thread
+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 implmented 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).
condition variables list into the run queue. Note that a mutex
must *not* be held while returning from a PP function.
-Perl locks are a condpair_t structure (a triple of a mutex, a
-condtion variable and an owner thread field) attached by 'm'
-magic to any SV. pp_lock locks such an object by waiting on the
-condition variable until the owner field is zero and then setting
-the owner field to its own thread pointer. The lock is 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, releasing the lock.
+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
https://perl5.git.perl.org / perl5.git / blobdiff