+++ /dev/null
-See README.alpha for Linux on DEC AXP info.
-
-This file applies mostly to Linux/Intel IA32. Ports to Linux on an M68K
-and PowerPC are also integrated. They should behave similarly, except that
-the PowerPC port lacks incremental GC support, and it is unknown to what
-extent the Linux threads code is functional. See below for M68K specific
-notes.
-
-Incremental GC is supported on Intel IA32 and M68K.
-
-Dynamic libraries are supported on an ELF system. A static executable
-should be linked with the gcc option "-Wl,-defsym,_DYNAMIC=0".
-
-The collector appears to work with Linux threads. We have seen
-intermittent hangs in sem_wait. So far we have been unable to reproduce
-these unless the process was being debugged or traced. Thus it's
-possible that the only real issue is that the debugger loses
-signals on rare occasions.
-
-The garbage collector uses SIGPWR and SIGXCPU if it is used with
-Linux threads. These should not be touched by the client program.
-
-To use threads, you need to abide by the following requirements:
-
-1) You need to use LinuxThreads (which are included in libc6).
-
- The collector relies on some implementation details of the LinuxThreads
- package. It is unlikely that this code will work on other
- pthread implementations (in particular it will *not* work with
- MIT pthreads).
-
-2) You must compile the collector with -DGC_LINUX_THREADS and -D_REENTRANT
- specified in the Makefile.
-
-3a) Every file that makes thread calls should define GC_LINUX_THREADS and
- _REENTRANT and then include gc.h. Gc.h redefines some of the
- pthread primitives as macros which also provide the collector with
- information it requires.
-
-3b) A new alternative to (3a) is to build the collector and compile GC clients
- with -DGC_USE_LD_WRAP, and to link the final program with
-
- (for ld) --wrap read --wrap dlopen --wrap pthread_create \
- --wrap pthread_join --wrap pthread_detach \
- --wrap pthread_sigmask --wrap sleep
-
- (for gcc) -Wl,--wrap -Wl,read -Wl,--wrap -Wl,dlopen -Wl,--wrap \
- -Wl,pthread_create -Wl,--wrap -Wl,pthread_join -Wl,--wrap \
- -Wl,pthread_detach -Wl,--wrap -Wl,pthread_sigmask \
- -Wl,--wrap -Wl,sleep
-
- In any case, _REENTRANT should be defined during compilation.
-
-4) Dlopen() disables collection during its execution. (It can't run
- concurrently with the collector, since the collector looks at its
- data structures. It can't acquire the allocator lock, since arbitrary
- user startup code may run as part of dlopen().) Under unusual
- conditions, this may cause unexpected heap growth.
-
-5) The combination of GC_LINUX_THREADS, REDIRECT_MALLOC, and incremental
- collection fails in seemingly random places. This hasn't been tracked
- down yet, but is perhaps not completely astonishing. The thread package
- uses malloc, and thus can presumably get SIGSEGVs while inside the
- package. There is no real guarantee that signals are handled properly
- at that point.
-
-6) Thread local storage may not be viewed as part of the root set by the
- collector. This probably depends on the linuxthreads version. For the
- time being, any collectable memory referenced by thread local storage should
- also be referenced from elsewhere, or be allocated as uncollectable.
- (This is really a bug that should be fixed somehow.)
-
-
-M68K LINUX:
-(From Richard Zidlicky)
-The bad news is that it can crash every linux-m68k kernel on a 68040,
-so an additional test is needed somewhere on startup. I have meanwhile
-patches to correct the problem in 68040 buserror handler but it is not
-yet in any standard kernel.
-
-Here is a simple test program to detect whether the kernel has the
-problem. It could be run as a separate check in configure or tested
-upon startup. If it fails (return !0) than mprotect can't be used
-on that system.
-
-/*
- * test for bug that may crash 68040 based Linux
- */
-
-#include <sys/mman.h>
-#include <signal.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-
-char *membase;
-int pagesize=4096;
-int pageshift=12;
-int x_taken=0;
-
-int sighandler(int sig)
-{
- mprotect(membase,pagesize,PROT_READ|PROT_WRITE);
- x_taken=1;
-}
-
-main()
-{
- long l;
-
- signal(SIGSEGV,sighandler);
- l=(long)mmap(NULL,pagesize,PROT_READ,MAP_PRIVATE | MAP_ANON,-1,0);
- if (l==-1)
- {
- perror("mmap/malloc");
- abort();
- }
- membase=(char*)l;
- *(long*)(membase+sizeof(long))=123456789;
- if (*(long*)(membase+sizeof(long)) != 123456789 )
- {
- fprintf(stderr,"writeback failed !\n");
- exit(1);
- }
- if (!x_taken)
- {
- fprintf(stderr,"exception not taken !\n");
- exit(1);
- }
- fprintf(stderr,"vmtest Ok\n");
- exit(0);
-}
-
-
projects / msp430-gcc.git / blobdiff