From owner-freebsd-arch Thu Mar 7 17:51:58 2002 Delivered-To: freebsd-arch@freebsd.org Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by hub.freebsd.org (Postfix) with ESMTP id 12D8C37B404 for ; Thu, 7 Mar 2002 17:51:54 -0800 (PST) Received: by elvis.mu.org (Postfix, from userid 1192) id CBF80AE1FC; Thu, 7 Mar 2002 17:51:53 -0800 (PST) Date: Thu, 7 Mar 2002 17:51:53 -0800 From: Alfred Perlstein To: Jeff Roberson Cc: julian@elischer.org, arch@freebsd.org Subject: Re: Contemplating THIS change to signals. (fwd) Message-ID: <20020308015153.GP26621@elvis.mu.org> References: <20020307195241.M64788-100000@mail.chesapeake.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020307195241.M64788-100000@mail.chesapeake.net> User-Agent: Mutt/1.3.27i Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG * Jeff Roberson [020307 16:57] wrote: > > > On Thu, 7 Mar 2002, Alfred Perlstein wrote: > > > > > * Alfred Perlstein [020307 16:25] wrote: > > > * Julian Elischer [020307 14:00] wrote: > > > > > > You are correct, you can _not_ allow arbitrary kernel threads to > > > block indefinetly while potentially holding higher level locks. > > > > > > Please proceed with your planned work, it seems like the right > > > thing to do. > > > > Both Poul-Henning Kamp and Nate Williams bring up the important > > point of potentially long running syscalls, there are two > > ways you might consider fixing this: > > > > 1) add an additional flag to msleep to allow suspension during sleep. > > 2) restart the syscall at the userland boundry. > > > > Wouldn't it be reasonable to ignore the stop until we return to the user? > This way we could continue to honor all other signals inside msleep, which > seems to be very desirable. We should just postpone the STOP until we > actually return to the user. > > Am I missing something? This is a good idea however you are missing something. We need to be able to unpost the STOP then that way when if while blocked in tsleep a STOP followed by a CONT is delivered we don't get the ordering wrong, either that or the underlying issig (or whatever) needs to make sure it processes STOPs before CONTs. I think at this point we should be looking at code and/or giving Julian some time to think about alternatives and the pitfalls of just waiting for the userret boundry. -- -Alfred Perlstein [alfred@freebsd.org] 'Instead of asking why a piece of software is using "1970s technology," start asking why software is ignoring 30 years of accumulated wisdom.' Tax deductible donations for FreeBSD: http://www.freebsdfoundation.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message