From: David Mosberger <davidm@napali.hpl.hp.com>
To: Ulrich Drepper <drepper@redhat.com>
Cc: davidm@hpl.hp.com, libc-hacker@sources.redhat.com
Subject: Re: fix ia64 longjmp() to work from alternate signal-stack
Date: Thu, 26 Aug 2004 09:37:00 -0000 [thread overview]
Message-ID: <16685.44908.144890.277988@napali.hpl.hp.com> (raw)
In-Reply-To: <412DAC31.1050404@redhat.com>
>>>>> On Thu, 26 Aug 2004 02:24:01 -0700, Ulrich Drepper <drepper@redhat.com> said:
Uli> David Mosberger wrote:
>> If there are no objections, please apply this patch.
Uli> I don't like this. The behavior of longjmp if the starting point is
Uli> using the alternate stack while the destination uses the normal stack,
Uli> is currently unspecified in POSIX. I've asked for clarification in the
Uli> POSIX working group. The result I expect is "don't do it", aka,
Uli> unspecified.
I wouldn't mind at all if that were the conclusion. I even thought
SuS left this unspecified, but upon rereading the spec, it seems SuS
explicitly allows this case. Can you let me know when you hear back?
Uli> For the unwind/cancellation handling this might not apply. But
Uli> it is an implementation decision to use setjmp/longjmp. So,
Uli> the solution should be to use special versions of those
Uli> interfaces in the nptl implementation. For all platforms but
Uli> ia64 the new names are just aliases of the normal code. For
Uli> ia64 this heavier code is used. This will also take care of
Uli> most of the performance penalties since they don't apply in
Uli> general, only in the thread code.
Couldn't we avoid the setjmp/longjmp altogether? On ia64, code
without unwind info is considered broken and since we unwind anyhow we
could have a C cleanup handler for start_thread() at almost zero cost.
That would obviate the need for setjmp() in start_thread() and might
even speed up thread-creation a little.
--david
next prev parent reply other threads:[~2004-08-26 9:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-25 16:39 David Mosberger
2004-08-26 9:24 ` Ulrich Drepper
2004-08-26 9:37 ` David Mosberger [this message]
2004-08-31 15:10 ` David Mosberger
2004-08-31 15:31 ` Ulrich Drepper
2004-08-31 16:14 ` David Mosberger
2004-08-31 16:20 ` Jakub Jelinek
2004-09-01 8:52 ` David Mosberger
2004-09-02 22:50 ` Ulrich Drepper
2004-09-07 17:36 ` David Mosberger
2004-09-13 17:36 ` David Mosberger
2004-09-13 18:39 ` Ulrich Drepper
2004-09-14 17:01 ` David Mosberger
2004-08-31 16:20 ` Ulrich Drepper
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