Date: Thu, 7 Mar 2002 17:51:53 -0800 From: Alfred Perlstein <bright@mu.org> To: Jeff Roberson <jroberson@chesapeake.net> Cc: julian@elischer.org, arch@freebsd.org Subject: Re: Contemplating THIS change to signals. (fwd) Message-ID: <20020308015153.GP26621@elvis.mu.org> In-Reply-To: <20020307195241.M64788-100000@mail.chesapeake.net> References: <E68F4182B5EFBE42A503F10FCB75FEDE04AD5B@EX1.midstream.com> <20020307195241.M64788-100000@mail.chesapeake.net>
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* Jeff Roberson <jroberson@chesapeake.net> [020307 16:57] wrote: > > > On Thu, 7 Mar 2002, Alfred Perlstein wrote: > > > > > * Alfred Perlstein <bright@mu.org> [020307 16:25] wrote: > > > * Julian Elischer <julian@elischer.org> [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
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