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See the README file for main Copyright notices.
DECthreads/MIT-pthreads extensions:
Copyright (c) 1995, 1996 by Ian Piumarta and INRIA, with permission
for use under exactly the same terms as the original GC; i.e...
THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
Permission is hereby granted to use or copy this program for any
purpose, provided the above notices are retained on all copies.
Permission to modify the code and to distribute modified code is
granted, provided the above notices are retained, and a notice that
the code was modified is included with the above copyright notice.
MODIFICATIONS
The pthreads extensions required the following GC source files to be
modified:
dyn_load.c
gc.h
gc_priv.h
misc.c
os_dep.c
test.c
The modified sections are clearly visible, being those affected by the
existence of the preprocessor symbols MIT_PTHREADS and DEC_PTHREADS.
No parts of the original sources outside these sections were modified.
The following files are new:
README.pthreads
dec_threads.c
mit_threads.c
The Makefile was also modified very slightly, to include the two new
source files in the OBJS and CSRCS lists.
GENERAL DESCRIPTION
The pthreads extensions allow the GC to be used with DECpthreads
(under Digital Unix, formerly DEC OSF/1) or the user-level
MIT-pthreads implementation by Chris Provenzano (running on a large
variety of platforms). DECthreads is bundled with DEC's Unix
machines; MIT-pthreads is available from:
ftp://sipb.mit.edu:/pub/pthreads
or ftp://toxicwaste.mit.edu:/pub/archive/pthreads
INSTALLATION AND PORTABILITY
These extensions have been tested (and appear to work) on the
following platforms:
DECthreads:
DEC Alpha OSF/1 3.2C/3.2D
MIT-pthreads (tested with pthreads versions 1.60 beta4 and beta5.9):
DEC Alpha OSF/1 3.2C/3.2D
Sparc SunOS 4.1.3/4.1.3_U1/4.1.4
i586 Red Hat Linux 3.0.3, Kernel 1.99.4
HP 9000/725 HP-UX A.09.05
Very minor additions may be needed to be make the extensions work with
the other architectures supported by both the GC and MIT-pthreads.
Note that some versions of gcc-2.7 are broken on DEC Alpha. Version
2.7.0 seems to be reliable, and versions 2.7.3 and later might be.
Unless you're already familiar with this GC:
Read the installtation notes in the README file!
Read the Makefile!
To install for DECpthreads:
Edit "Makefile.pthreads". Uncomment the definition "THR=DEC".
Edit (if necessary) the definitions immediately following the
comment "Definitions for DECthreads" to use the correct
compiler and/or CFLAGS for your environment. See Makefile for
an explanation of the GC-related flags.
If you are using gcc rather than the DEC C compiler, edit the
Makefile and remove the line indicated in the target
"mark_rts.o".
Type "make -f Makefile.pthreads" to build the basic library
and gctest program, with pthreads support.
Run gctest to check that things are working.
If you require C++ support, type "make -f Makefile.pthreads
c++ THR=DEC". Make sure the test_cpp program does not fail.
To install for MIT-pthreads:
Install (if necessary) the MIT-pthreads package (see above).
Versions 1.60beta4 and earlier have a broken "pg++" script
(later versions may be corrected): if necessary change the
definition of "libs" from
libs='-lpthread -lstdc++ -lm -lgcc'
to
libs='-lpthread -lstdc++ -lm -lgcc -lpthread'
Edit "Makefile.pthreads". Uncomment the definition "THR=MIT".
Edit (if necessary) the definitions immediately following the
comment "Definitions for MIT-pthreads" to use the correct
CFLAGS for your environment (the supplied compiler definitions
should be correct in most situations). See Makefile for an
explanation of the GC-related flags.
If you are compiling on a DEC Alpha using gcc rather than the
DEC C compiler, edit the Makefile and remove the line
indicated in the target "mark_rts.o".
Type "make -f Makefile.pthreads" to build the basic library
and gctest program, with pthreads support.
Run gctest to check that things are working.
If you require C++ support, type "make -f Makefile.pthreads
c++ THR=MIT". Make sure the test_cpp program does not fail.
MODIFICATIONS TO THE PTHREADS INTERFACES
The extensions rely on intercepting calls to a few pthreads routines.
Any source file using the pthreads routines MUST include "gc.h", even
if there is no GC-related code in the file.
The following DECthreads routines are affected:
int pthread_create(pthread_t *thread, pthread_attr_t attr,
pthread_startroutine_t start_routine,
pthread_addr_t arg);
int pthread_detach(pthread_t *thread);
The following MIT-pthreads routines are affected:
int pthread_create(pthread_t *thread, pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg);
BUGS
Incremental mode does not work with DECpthreads. The reasons are not
yet fully explored. GC_enable_incremental() is therefore a no-op when
the GC is compiled with DECpthreads support.
The DECthreads extensions assume a one-to-one correspondance between
each pthread and a kernel (mach) thread. This appears to be true with
round-robin scheduling, but may not be true for other scheduling
policies. (This concerns stopping the world: there is no documented
mechanism to stop the pthreads world, so we have to stop the
underlying kernel threads instead [which is documented]. When asked
about setting the pthreads kernel lock, all that the DEC techincal
people would tell me was: "don't meddle with things that you don't
understand".)
The extensions have been tested with both versions of pthreads,
although in relatively undemanding situations. Some subtle problems
may still exist in programs which use thread synchronisation
operations (pthread_join/pthread_detach) in bizarre ways, or which use
scheduling policies other than the default round-robin. The more
exotic pthread routines (e.g. executing a call on another thread's
stack) have not been tested very much at all.
The MITpthreads extensions rely on snooping about in small parts of
the pthreads' private internal structures. This seems unavoidable.
The extensions appear to work with unmodified versions of the GNU
libgcc and libstdc++ (at least as far as iostreams are concerned), but
large parts of these libraries remain untested in a pthreads/GC
context.
BUG REPORTS AND SUGGESTIONS FOR IMPROVEMENTS
Should be sent to: Ian.Piumarta@inria.fr
It would be most helpful if you could include a small program which
reproduces the bug.
ACKNOWLEDGEMENTS
I am immensely grateful to David Halls (David.Halls@cl.cam.ac.uk) who
spent many months "alpha testing" the extensions, suffering problems
with the early implementations, and contributing suggestions for
improvements. He also kindly tested the MIT-pthreads extensions under
Linux and provided the code specific to dynamic loading and the HP-PA
architecture.
------------------------------- projet SOR -------------------------------
Ian Piumarta, INRIA Rocquencourt, Internet: Ian.Piumarta@inria.fr
BP105, 78153 Le Chesnay Cedex, FRANCE Voice: +33 1 39 63 52 87
----------------------- Systemes a Objets Repartis -----------------------
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