diff options
Diffstat (limited to 'boehm-gc/README.linux')
| -rw-r--r-- | boehm-gc/README.linux | 30 |
1 files changed, 24 insertions, 6 deletions
diff --git a/boehm-gc/README.linux b/boehm-gc/README.linux index b4f136a..e35e712 100644 --- a/boehm-gc/README.linux +++ b/boehm-gc/README.linux @@ -31,16 +31,28 @@ To use threads, you need to abide by the following requirements: 2) You must compile the collector with -DLINUX_THREADS and -D_REENTRANT specified in the Makefile. -3) Every file that makes thread calls should define LINUX_THREADS and +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. -4) Currently dlopen() is probably not safe. The collector must traverse - the list of libraries maintained by the runtime loader. That can - probably be an inconsistent state when a thread calling the loader is - is stopped for GC. (It's possible that this is fixable in the - same way it is handled for SOLARIS_THREADS, with GC_dlopen.) +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 @@ -48,3 +60,9 @@ To use threads, you need to abide by the following requirements: 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.) |