From: "H . J . Lu" <hjl@valinux.com>
To: Geoff Keating <geoffk@cygnus.com>
Cc: libc-hacker@sourceware.cygnus.com
Subject: Re: A patch for linuxthreads
Date: Thu, 16 Dec 1999 16:43:00 -0000 [thread overview]
Message-ID: <19991216164305.A11873@valinux.com> (raw)
In-Reply-To: <199912170033.QAA01416@localhost.cygnus.com>
On Thu, Dec 16, 1999 at 04:33:18PM -0800, Geoff Keating wrote:
> > Date: Thu, 16 Dec 1999 16:12:43 -0800
> > From: "H . J . Lu" <hjl@valinux.com>
> >
> > Hi,
> >
> > While working on the ia64 port for linuxthreads, I found
> > this patch was necessary. Any comments?
>
> Yes.
>
> > --
> > H.J. Lu (hjl@gnu.org)
> > ---
> > Thu Dec 16 15:59:58 1999 H.J. Lu <hjl@gnu.org>
> >
> > * manager.c (pthread_allocate_stack): Correct the calculation
> > of "new_thread_bottom".
> >
> > Index: manager.c
> > ===================================================================
> > RCS file: /work/cvs/gnu/glibc-2.1/linuxthreads/manager.c,v
> > retrieving revision 1.1.1.22
> > diff -u -p -r1.1.1.22 manager.c
> > --- manager.c 1999/11/27 18:44:03 1.1.1.22
> > +++ manager.c 1999/12/17 00:10:18
> > @@ -291,7 +291,7 @@ static int pthread_allocate_stack(const
> > {
> > /* Allocate space for stack and thread descriptor at default address */
> > new_thread = default_new_thread;
> > - new_thread_bottom = (char *) new_thread - STACK_SIZE;
> > + new_thread_bottom = (char *) (new_thread + 1) - STACK_SIZE;
> > if (mmap((caddr_t)((char *)(new_thread + 1) - INITIAL_STACK_SIZE),
> > INITIAL_STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
> > MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | MAP_GROWSDOWN,
> >
>
> 1. When you submit a patch, it is helpful if you explain what bug you
> are fixing or what new feature you are adding. This saves us from
> having to deduce it by inspection of the code. This is even more
> important when you are implementing on hardware that is not readily
> available.
I am not sure how much I am allowed to say. Let me just say we
need to access new_thread_bottom. If I understand the code
correctly, the stack top is (char *)(new_thread + 1) since we do
if (mmap((caddr_t)((char *)(new_thread + 1) - INITIAL_STACK_SIZE),
INITIAL_STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | MAP_GROWSDOWN,
That means we mmap the top INITIAL_STACK_SIZE bytes from the stack
top and grow the stack downwards. If it is true, the stack bottom should
be
(char *)(new_thread + 1) - STACK_SIZE
We didn't see any bug reports since not many archs need to access
the stack bottom. In fact, if you compute it,
(char *) new_thread - STACK_SIZE
usually is not page aligned.
>
> 2. If you need to change this, don't you need to change the similar
> calculation in the previous {} group a few lines above?
It is because the user should provide the correct stack top and
stack size.
--
H.J. Lu (hjl@gnu.org)
next prev parent reply other threads:[~1999-12-16 16:43 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-16 16:12 H . J . Lu
[not found] ` <199912170033.QAA01416@localhost.cygnus.com>
1999-12-16 16:43 ` H . J . Lu [this message]
-- strict thread matches above, loose matches on Subject: below --
2000-09-04 10:48 H . J . Lu
2000-09-04 19:54 ` Ulrich Drepper
1999-04-14 22:31 H.J. Lu
1999-04-14 23:51 ` Ulrich Drepper
1999-03-17 13:44 Mike Stump
1999-03-18 7:44 ` H.J. Lu
1999-03-16 20:28 H.J. Lu
1999-03-17 2:20 ` Mark Kettenis
1999-03-17 7:21 ` H.J. Lu
1999-03-17 4:52 ` Andrey Slepuhin
1998-12-02 10:35 H.J. Lu
1998-12-02 11:44 ` Ulrich Drepper
1998-10-24 18:33 H.J. Lu
1998-10-25 0:59 ` Ulrich Drepper
1998-10-25 8:22 ` H.J. Lu
1998-10-25 8:22 ` Ulrich Drepper
1998-08-08 23:26 H.J. Lu
1998-08-09 8:59 ` Ulrich Drepper
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