mirror of
git://gcc.gnu.org/git/gcc.git
synced 2024-12-31 02:24:40 +08:00
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.
|
|
|
|
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.
|
|
|
|
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 -DLINUX_THREADS and -D_REENTRANT
|
|
specified in the Makefile.
|
|
|
|
3a) Every file that makes thread calls should define 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 with
|
|
-DUSE_LD_WRAP, and to link the final program with
|
|
|
|
(for ld) --wrap read --wrap dlopen --wrap pthread_create \
|
|
--wrap pthread_join --wrap pthread_sigmask
|
|
|
|
(for gcc) -Wl,--wrap -Wl,read -Wl,--wrap -Wl,dlopen -Wl,--wrap \
|
|
-Wl,pthread_create -Wl,--wrap -Wl,pthread_join -Wl,--wrap \
|
|
-Wl,pthread_sigmask
|
|
|
|
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 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.)
|