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Date:      Tue, 22 May 2001 18:04:24 -0700 (PDT)
From:      John Baldwin <jhb@FreeBSD.ORG>
To:        John Baldwin <jhb@FreeBSD.ORG>
Cc:        current@FreeBSD.ORG, Alfred Perlstein <bright@rush.net>
Subject:   RE: HEADS UP: I broke swapping
Message-ID:  <XFMail.010522180424.jhb@FreeBSD.org>
In-Reply-To: <XFMail.010522163307.jhb@FreeBSD.org>

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On 22-May-01 John Baldwin wrote:
> 
> On 20-May-01 Alfred Perlstein wrote:
>> I broke swapping with the vm mutex.
>> 
>> Hopefully I should have this fixed up within a couple of days tops.
>> 
>> No, I'm not heading off to Aruba or someplace after this intrusive
>> change, I am working on it.  Your kernel may panic, but I hope you
>> all keep a level head about this and don't follow suit. :)
>> 
>> Patches, suggestions and crashdumps would be helpful.
>> 
>> Bruce has been giving me some helpful tracebacks that I'm planning
>> to use to stabilize the system.
> 
> I am currently running X on my laptop with a current kernel with the patch
> http://www.FreeBSD.org/~jhb/patches/vm.patch.  It is swapping, and I've
> tested
> out exhausting all the swap and mem at least which worked.

Well, I've cleaned out all but one lock order reversal (the race between
faultin() and swapout() needs to be fixed in a more proper fashion) and tried
to push Giant back down some by re-enabling all the MPSAFE syscalls in Alfred's
commit, but now I can deadlock (well, livelock actually) my laptop in single
user via a simple memkill program that basically does this:

        for (;;)
                *(char *)malloc(1) = 1;

If I have swap (i.e. I've run swapon on a swap partition) the program is killed
by the system fine.  If I don't have swap, then both the memkill process adn
the swapper process (proc0) are stuck in the "vmwait" wait channel used by
VM_WAIT.  Any ideas?

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.Baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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