Date: Fri, 15 Nov 2002 09:43:29 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: Doug Rabson <dfr@nlsystems.com> Cc: ia64@FreeBSD.ORG Subject: Re: setjmp/longjmp and libc_r [was: Re: cvs commit: src/lib/libc/ia64/gen _setjmp.S] Message-ID: <20021115174328.GA4288@dhcp01.pn.xcllnt.net> In-Reply-To: <200211150909.32267.dfr@nlsystems.com> References: <200211140640.gAE6eNq9016231@repoman.freebsd.org> <200211141951.41202.dfr@nlsystems.com> <20021114143809.A31710@kayak.xcllnt.net> <200211150909.32267.dfr@nlsystems.com>
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On Fri, Nov 15, 2002 at 09:09:32AM +0000, Doug Rabson wrote: > > > > > > I've managed to reload my memory from magtape :-). To use > > > setjmp/longjmp for thread switching, you would need to call flushrs > > > from setjmp. That would simplify longjmp at the cost of severely > > > pessimising setjmp. > > > > This is exactly what we now have and what I'm willing to sacrificy at > > this time. It's easy enough to optimize setjmp/longjmp once we have > > the *context stuff. > > This is totally wrong. No, it's a step in different direction than you would have chosen. Pick your words with care. See also below. > > Note that I'm still not convinced that not doing a flushrs in setjmp > > will work when a signal handler on the alternate stack jumps to the > > saved context on the regular stack. You cannot compare the saved > > ar.bsp or ar.bspstore with the current ar.bspstore without taking > > into account that they may not be on the same register stack. > > The signal trampoline performs the flushrs when it switches stacks. Ah, I see. You avoid having the dirty registers on the kernel stack by doing an exception restore to the original stack, do a flushrs and then switch to the alternate stack. I wondered about this hoop-jumping... > For libc_r with the code written this way, you can probably still do > thread switching without swapcontext(2) by adding an explicit flushrs > before the call to setjmp(3). It would be less effort to write the > support for userland or kernel swapcontext though. I've been looking at that. If by implementing the *context functions we speed-up the adoption of *context by libc_r, then I'm willing to spend time on it. What I don't want is spending time on *context and in the end not have libc_r, due to it not being changed to use it. Thus: I want people to sign-up for a libc_r that uses *context before 5.0-RELEASE, but preferrably tomorrow. A well-intended timeline would be very nice... -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-ia64" in the body of the message
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