Date: Wed, 15 Aug 2012 11:21:34 -0400 From: John Baldwin <jhb@freebsd.org> To: Sergey Kandaurov <pluknet@gmail.com> Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, freebsd-current FreeBSD <freebsd-current@freebsd.org>, des@freebsd.org Subject: Re: swp_pager_meta_build DoS printf Message-ID: <201208151121.34815.jhb@freebsd.org> In-Reply-To: <CAE-mSO%2BXH36yyvSyaHU7bNAzDS___C=zwriAaeT6p6itbbKYNw@mail.gmail.com> References: <7BEE3948-EE35-48C2-B4B1-25E34087A4C4@lists.zabbadoz.net> <B60059D0-9ED8-430D-8D7D-275E4536AC94@lists.zabbadoz.net> <CAE-mSO%2BXH36yyvSyaHU7bNAzDS___C=zwriAaeT6p6itbbKYNw@mail.gmail.com>
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On Monday, August 13, 2012 1:49:38 am Sergey Kandaurov wrote:
> On 2 July 2012 20:31, Bjoern A. Zeeb <bzeeb-lists@lists.zabbadoz.net> wrote:
> >
> > On 2. Jul 2012, at 14:36 , John Baldwin wrote:
> >
> >> On Sunday, July 01, 2012 8:23:31 am Bjoern A. Zeeb wrote:
> >>> Hey,
> >>>
> >>> hitting this printf in swp_pager_meta_build()
> >>>
> >>> if (uma_zone_exhausted(swap_zone)) {
> >>> printf("swap zone exhausted, increase
kern.maxswzone\n");
> >>> vm_pageout_oom(VM_OOM_SWAPZ);
> >>> pause("swzonex", 10);
> >>> } else
> >>>
> >>> seems to be an effective way to put the machine into a state of no
recovery
> >>> unless the memory situation would be able to clear itself. Not that it
wouldn't
> >>> otherwise be any better but in addition having a couple of tenthousands
of these
> >>> going to console as well is really not helpful to try to do anything
either. Can
> >>> we make it a log() call or something?
> >>>
> >>> /bz
> >>>
> >>> PS: I am not sure as I have seen it on someone else's machines and it's
> >>> probably been ZFS that caused it. I unfortunately neither had a way to
> >>> get back in or break to a kernel debugger, so information is sparse.
> >>
> >> This used to be a silent deadlock before I added the printf() and the
call to
> >> OOM. :-P Do you just want to ratelimit the printf? We have an API to
ratelimit
> >> printf's already.
> >
> > Ratelimit would be fine; I was writing that on the wrong time of the
wrong day to
> > just get it out; could you do that?
>
> Hi, looks like the discussion was abandoned.
> What about this patch? It enables to ratelimit the printf.
> Also, are the new variables put in the right places from the style pov?
I think DES has a newer variant of this now?
--
John Baldwin
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