[3546] in linux-scsi channel archive
Re: SMP 2.1.90-pre3 SCSI kernel panic
daemon@ATHENA.MIT.EDU (sistema@readysoft.es)
Tue Mar 17 05:57:08 1998
Date: Tue, 17 Mar 1998 11:54:31 +0100 (MET)
From: sistema@readysoft.es
To: dledford@dialnet.net
cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <350E47B9.3B2F001A@dialnet.net>
On 17 Mar, Doug Ledford wrote:
>>
>> 2.1.90-pre doesnŽt recover from all the errors and finally the system
>> locks up; iŽts not a hrd lock as I can use the magic keys, but I canŽt
>> even shutdown the machine.
>
> I would say both of these are merely different symptoms of the same
> problem. Namely, when a swap sector is bad and data can't be swapped back
> in, the system is pretty well screwed. We've written something we expected
> to be able to get back (and indeed have to be able to get back in order to
> continue) and now we find out we can't. It's no better than trying to
> compile kernels on a machine with bogus RAM that causes gcc to give SIG 11
> errors all of the time.
Ok, so it looks like 2.1 more agressive swapping awakes more easyly
this kind of problem. But, anyway, error conditions in 2.0.33 look like
better supported as the system never locks up. And it canŽt be
casuality that 2.1 always hangs and 2.0.33 never.
> Secondly, there are a lot of drives out there with firmware that starts to
> flake out if the error is bad enough. Some of the drives I've seen in the
> recent past would completely wedge the entire SCSI bus so hard that the only
> solution was to power down the system before it would work again when it hit
> particularly bad portions of the disk.
It is a Seagate:
Host: scsi1 Channel: 00 Id: 00 Lun: 00
Vendor: SEAGATE Model: ST15230W Rev: 0298
Type: Direct-Access ANSI SCSI revision: 02
I low-level formatted it to catch defective sectors a couple of months
ago.
>> My conclusions
>> --------------
>> ThereŽs something wrong in the SCSI error recovery in 2.1.89 and
>> greater kernels.
>
> When you get a bad sector in a swap partition that you've already written
> info to, there is *no* good recovery method. The best case scenario is you
> kill a program or two and go on, the worst case scenario is all hell breaks
> loose because programs are passing all kinds of bogus data, and the kernel
> itself could have data there (specifically, things like the vmalloc call in
> net/unix come to mind as things that have swappable kernel mem, but I could
> be wrong if vmalloc doesn't actually give you swappable mem, I haven't
> looked into it but I was under the impression that it does).
Agree.
>> IŽll turn on debugging this midday, with 2.1.90-pre3 and see what I get.
>>
>> Thanks for your interest.
>> Pau
>
> You can try debugging, and we can try to make the system more resilient, but
> the bottom line is, if you have bad sectors in a swap partition that aren't
> going away with the AWRE and ARRE bits set on the drive, then you either
> have to quit using that partition or low level format the drive and hope
> they don't come back. There are certain things that simply can not be
> worked around in a sane manner without building hardware that has every
> single circuit and bit duplicated in one place or another (and does that
> even qualify as sane?)
IŽll check if the are spare sectors for the remapping, otherwise IŽll
try to low-level format it again.
Anyway, it looks like thereŽs something in 2.0.33 related to error
conditions that works better thna in 2.1.89.
If I can help to detect it IŽll do my best.
Thanks
Pau
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