93002327db
* acinclude.m4: Bump version to 5.0a6. * configure.in: Don't use alpha_mach_dep.s. * include/private/config.h, irix_threads.c gc_watcom.asm: Delete obsolete files. From-SVN: r33251
69 lines
3.1 KiB
Plaintext
69 lines
3.1 KiB
Plaintext
See README.alpha for Linux on DEC AXP info.
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This file applies mostly to Linux/Intel IA32. Ports to Linux on an M68K
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and PowerPC are also integrated. They should behave similarly, except that
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the PowerPC port lacks incremental GC support, and it is unknown to what
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extent the Linux threads code is functional.
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Incremental GC is supported on Intel IA32 and M68K.
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Dynamic libraries are supported on an ELF system. A static executable
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should be linked with the gcc option "-Wl,-defsym,_DYNAMIC=0".
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The collector appears to work with Linux threads. We have seen
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intermittent hangs in sem_wait. So far we have been unable to reproduce
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these unless the process was being debugged or traced. Thus it's
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possible that the only real issue is that the debugger loses
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signals on rare occasions.
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The garbage collector uses SIGPWR and SIGXCPU if it is used with
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Linux threads. These should not be touched by the client program.
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To use threads, you need to abide by the following requirements:
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1) You need to use LinuxThreads (which are included in libc6).
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The collector relies on some implementation details of the LinuxThreads
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package. It is unlikely that this code will work on other
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pthread implementations (in particular it will *not* work with
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MIT pthreads).
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2) You must compile the collector with -DLINUX_THREADS and -D_REENTRANT
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specified in the Makefile.
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3a) Every file that makes thread calls should define LINUX_THREADS and
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_REENTRANT and then include gc.h. Gc.h redefines some of the
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pthread primitives as macros which also provide the collector with
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information it requires.
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3b) A new alternative to (3a) is to build the collector with
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-DUSE_LD_WRAP, and to link the final program with
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(for ld) --wrap read --wrap dlopen --wrap pthread_create \
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--wrap pthread_join --wrap pthread_sigmask
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(for gcc) -Wl,--wrap -Wl,read -Wl,--wrap -Wl,dlopen -Wl,--wrap \
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-Wl,pthread_create -Wl,--wrap -Wl,pthread_join -Wl,--wrap \
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-Wl,pthread_sigmask
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In any case, _REENTRANT should be defined during compilation.
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4) Dlopen() disables collection during its execution. (It can't run
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concurrently with the collector, since the collector looks at its
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data structures. It can't acquire the allocator lock, since arbitrary
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user startup code may run as part of dlopen().) Under unusual
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conditions, this may cause unexpected heap growth.
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5) The combination of LINUX_THREADS, REDIRECT_MALLOC, and incremental
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collection fails in seemingly random places. This hasn't been tracked
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down yet, but is perhaps not completely astonishing. The thread package
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uses malloc, and thus can presumably get SIGSEGVs while inside the
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package. There is no real guarantee that signals are handled properly
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at that point.
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6) Thread local storage may not be viewed as part of the root set by the
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collector. This probably depends on the linuxthreads version. For the
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time being, any collectable memory referenced by thread local storage should
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also be referenced from elsewhere, or be allocated as uncollectable.
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(This is really a bug that should be fixed somehow.)
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