Date: Thu, 8 Jul 1999 15:34:25 -0300 (ADT) From: The Hermit Hacker <scrappy@hub.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: freebsd-current@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG Subject: Re: Known MMAP() race conditions ... ? Message-ID: <Pine.BSF.4.05.9907081532530.4088-100000@thelab.hub.org> In-Reply-To: <199907081458.HAA40125@apollo.backplane.com>
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On Thu, 8 Jul 1999, Matthew Dillon wrote:
> :At that time, Matt pop'd up and stated that he knew of *at least* 6 MMAP()
> :related race conditions that he was hoping to be able to get fixed "within
> :a week"...that would have been two weeks ago.
>
> I think I was talking about mmap w/ NFS.
>
> Under FreeBSD-current I know of two problems ( though I could be
> forgetting some ) - there is a problem when a lot of pages get dirtied
> that can cause a low-memory deadlock to occur, and I believe there is a
> problem when mlock() or madvise() is used though I haven't reproduced
> it yet.
>
> Under FreeBSD-stable there are a number of additional, but minor problems
> related to visibility of non-zero garbage after file EOF in an mmap(),
> but these would have no effect on INN.
>
> What we need to know is why the machines are locking up. The usual
> way to figure this out is to compile the kernel up with DDB and then
> when it locks up ctl-alt-esc on the console to get the DDB prompt,
> and do a 'ps' to see what the procsses are blocked in.
No matter how much I want to get this fixed, I don't haven't yet been able
to get DDB to dump properly :( I've tried various things wiht the
portmaster that the serial console is attached to, but its either an old
ComOS on that machine, or they've "secured" it up against the various work
arounds :(
and...my server does this once a day, so would be a perfect candidate for
debugging :(
Marc G. Fournier ICQ#7615664 IRC Nick: Scrappy
Systems Administrator @ hub.org
primary: scrappy@hub.org secondary: scrappy@{freebsd|postgresql}.org
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