Date: Sun, 17 Nov 2002 14:01:02 +0000 From: Doug Rabson <dfr@nlsystems.com> To: Alfred Perlstein <bright@mu.org> Cc: Marcel Moolenaar <marcel@xcllnt.net>, Daniel Eischen <eischen@pcnet1.pcnet.com>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/lib/libc_r/arch/ia64 _atomic_lock.S Message-ID: <200211171401.02376.dfr@nlsystems.com> In-Reply-To: <20021117131358.GK6882@elvis.mu.org> References: <20021116185125.GB618@dhcp01.pn.xcllnt.net> <200211171025.00359.dfr@nlsystems.com> <20021117131358.GK6882@elvis.mu.org>
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On Sunday 17 November 2002 1:13 pm, Alfred Perlstein wrote: > * Doug Rabson <dfr@nlsystems.com> [021117 02:25] wrote: > > On Saturday 16 November 2002 7:58 pm, Marcel Moolenaar wrote: > > > On Sat, Nov 16, 2002 at 02:13:19PM -0500, Daniel Eischen wrote: > > > > On Sat, 16 Nov 2002, Marcel Moolenaar wrote: > > > > > If you want me to send patches, let me know. I'm trying to > > > > > figure out what to do now that the *context functions have > > > > > been turned into syscalls. It complicates things... > > > > > > > > I'm working on converting libc_r to use *context() so don't > > > > worry about doing it yourself. > > > > > > Cool! > > > > > > I hope to have the *context syscalls next week. I've decided to > > > not attack the problem head on, because we don't have time to > > > fix the infrastructure for it (we need to unwind to recreate the > > > context). Instead, I hope to hack-up a workable solution from an > > > ABI breaking change. The ABI breaker allows us to have > > > lightweight syscalls, which we permanently want. So, doing that > > > now is very attractive. The intend is to implement the *context > > > syscalls as lightweight syscalls in a very hackish way. This > > > serves as an experiment as well as solving an immediate problem. > > > Let's hope it works out... > > > > So you intend to recognise the context calls in the syscall wrapper > > and special-case them? This would work but it would also work for > > heavyweight syscalls. I'm still worried about how you are going to > > flush the user's register stack safely from kernel mode. > > I'm probably being dense, but doesn't the ABI specify behaviour > such that one may not use stack space past the frame pointer > (equivelant of ebp on i386) so this should be doable, right? > > Basically, as long as the frame pointer is moved before the > space is used it's safe, right? This is a bit different - I'm talking about the ia64's register stack,=20 as distinct from its normal stack. When switching from one thread to=20 another, you must flush any dirty registers into the old thread's=20 register stack backing memory. Doing this from kernel mode can be=20 tricky since the pages of backing memory might not be valid yet. --=20 Doug Rabson=09=09=09=09Mail: dfr@nlsystems.com =09=09=09=09=09Phone: +44 20 8348 6160 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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