libgcj and the NPTL posix threads implementation

Mon Mar 1 22:16:00 GMT 2004

I'm a bit confused, in part because I'm an X86 assembly amateur.
I assume both of the proposals below retrieve a value stored at an offset from
%gs? (What's "move"? Is it different from "mov" or a typo?) Won't %gs itself do as
a thread-specific value? Doesn't that always point to a thread-specific
area, independent of the thread package and tls implementation?
Hans
> -----Original Message-----
> From: Anthony Green [mailto:green@redhat.com]
> Sent: Monday, March 01, 2004 2:00 PM
> To: Jeff Sturm
> Cc: Boehm, Hans; 'Michael Koch'; java@gcc.gnu.org
> Subject: RE: libgcj and the NPTL posix threads implementation
>>> On Mon, 2004年03月01日 at 13:08, Jeff Sturm wrote:
> > On 2004年2月29日, Anthony Green wrote:
> > > + inline _Jv_ThreadId_t
> > > + _Jv_ThreadSelf (void)
> > > + {
> > > + size_t id;
> > > + asm ("mov %%gs:0x8, %0" : "=r"(id));
> > > + return id;
> > > + }
> > 
> > I'm curious what the special significance of offset 0x8 might be.
>> I believe that returns the posix thread ID, however, as you say...
>> > As I
> > understand TLS on glibc, "move %gs:0, %eax" would place the 
> thread pointer
> > in %eax, which is sufficient for these purposes as a 
> pointer to an opaque
> > per-thread structure.
>> Yes, that would work as well.
>> AG
>> -- 
> Anthony Green <green@redhat.com>
> Red Hat, Inc.
>