From owner-p4-projects Wed Apr 10 12:20:12 2002 Delivered-To: p4-projects@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 32767) id 4F28437B41C; Wed, 10 Apr 2002 12:20:00 -0700 (PDT) Delivered-To: perforce@freebsd.org Received: from anchor-post-35.mail.demon.net (anchor-post-35.mail.demon.net [194.217.242.93]) by hub.freebsd.org (Postfix) with ESMTP id E09BC37B400; Wed, 10 Apr 2002 12:19:58 -0700 (PDT) Received: from mailgate.nlsystems.com ([62.49.251.130] helo=herring.nlsystems.com) by anchor-post-35.mail.demon.net with esmtp (Exim 3.35 #1) id 16vNdN-0002SQ-0Z; Wed, 10 Apr 2002 20:19:57 +0100 Received: from salmon.nlsystems.com (salmon [10.0.0.3]) by herring.nlsystems.com (8.12.2/8.11.2) with ESMTP id g3AJJv3I014886; Wed, 10 Apr 2002 20:19:57 +0100 (BST) (envelope-from dfr@nlsystems.com) Date: Wed, 10 Apr 2002 20:19:56 +0100 (BST) From: Doug Rabson To: Peter Wemm Cc: Jake Burkholder , John Baldwin , Perforce Change Reviews Subject: Re: PERFORCE change 9504 for review In-Reply-To: <20020410191220.92F753810@overcee.wemm.org> Message-ID: <20020410201934.D16912-100000@salmon.nlsystems.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-p4-projects@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Wed, 10 Apr 2002, Peter Wemm wrote: > Doug Rabson wrote: > > On Wed, 10 Apr 2002, Jake Burkholder wrote: > > > > > Apparently, On Wed, Apr 10, 2002 at 09:06:18AM -0400, > > > John Baldwin said words to the effect of; > > > > > > > > > > > On 10-Apr-2002 Peter Wemm wrote: > > > > > http://people.freebsd.org/~peter/p4db/chv.cgi?CH=9504 > > > > > > > > > > Change 9504 by peter@peter_thunder on 2002/04/10 04:51:36 > > > > > > > > > > Use dfr's fix instead of my hack. I expect he'll commit this to > > > > > freefall soon. :-) > > > > > > > > Yep, much better. :) > > > > > > Well, now the flag checking code is duplicated in both the trap and syscall > > > return paths, alpha is the same. One wonders if the FRAME_SYSCALL optimiza > tion > > > is actually worth all this complication. > > > > I think its still worth it - it still does a lot less work in the common > > case. Bear in mind that calling ast() is quite rare and being forced to do > > a full exception restore (e.g. for a signal) is even rarer. A harmless > > extra call to ast() in that case is unlikely to be noticable. Having said > > that, for ia64 at least, it should be possible for the syscall to bypass > > the ast() bits at the beginning of exception_restore(). As long as syscall > > sets (p1,p2) to (1,0), it can jump to label 2 in exception_restore. > > John asked an awkward question a while ago.. What happens if the ast() > call in the back of the fast syscall return path changes the frame type? > eg: it posted a signal and turned off the FRAME_SYSCALL bit. We'll continue > with the fast return, right? Is this good or bad? Nonono. We check the frame type *after* the call to ast()... -- Doug Rabson Mail: dfr@nlsystems.com Phone: +44 20 8348 6160 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe p4-projects" in the body of the message