There is some code in earlier versions of the GC to do thread registration, but it's very platform specific and thus ugly. I think there wasn't a real facility for Linux. The tricky part of doing this in general is that the GC needs to know the stack bounds for the newly registered thread. It can find the hot end, but the cold end is often hard. GC7 addresses this by providing two ways to get the cold stack end: 1) A generic mechanism that just takes the address of a local. The collector knows how to implement that everywhere. We just provide a function that calls back one of your functions f with a stack address that's guaranteed to be "below" f. Since this is not the actual base of the stack, the GC ends up tracing pointers only in "new" frames. 2) A separate routine that tries to discover the stack base in a platform dependent way. It may fail. (And currently usually does.) I think that for Linux, pthread_getattr_np works for most threads, though perhaps not the main one. (The thread pointer also probably works in many cases.) I'm not sure the JNI primitives can be implemented in terms of (1). Certainly if you use CNI that has different semantics, in that the GC doesn't see pointers "below" you on the stack. We may need (2) to work for gcj. Hans > -----Original Message----- > From: Robin Green [mailto:greenrd@xxxxxxxxxxx] > Sent: Thursday, July 28, 2005 1:51 PM > To: Anthony Green; Boehm, Hans > Cc: tromey@xxxxxxxxxx; Discussion list for java related > Fedora development > Subject: RE: [fedora-java] rssowl: libgcj bugs that need > fixing for it torun > > > > On Thu, 2005-07-28 at 11:34 -0700, Boehm, Hans wrote: > > > [I missed the beginning of this thread initially.] > > > > > > I'm actually trying to work on some of these issues. Some status: > > > > Cool. > > > > Robin - is there a local hack/patch we can apply to swt > and/or rssowl > > to work around this problem until a real fix from Hans > migrates into > > GCC? > > I'm a bit out of my depth here. > > Hans wrote: "Gc7 (even the released, but very experimental > alpha3 version) has a thread registration interface." This > implies that the version in gcc _doesn't_ have a thread > registration interface, or anything that could be hacked > together into one. Is that surmise correct? > > If so, the only other thing I can think of is to spawn a new > registered thread instead of calling AttachCurrentThread, and > somehow translate all C->Java invocations on the unregistered > thread into inter-thread calls onto the new registered > thread. In other words, keep all Java code on a separate thread. Yuck. > > -- > Robin >
