Linux-kernel mailing list archive 1999-20,: Re: New partition type

# Re: New partition type

Ralf Baechle (ralf@gnu.org)
Thu, 13 May 1999 10:10:48 +0200

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On Tue, May 11, 1999 at 12:34:02PM +1000, Keith Owens wrote:

> Even with poll instead of interrupts, all SCSI code is going to use the
> buffer cache and try to get the io request spin lock. During Oops
> dumping, neither are safe. If the Oops occurred during earlier I/O
> processing and we do *any* disk I/O from Oops recovery then we are
> violating all the constraints on I/O reentrancy. If we are lucky we just
> hang on a spin lock, if we are unlucky we corrupt kernel structures and
> make the problem worse.
>
> The only safe method of doing I/O inside Oops recovery is one that does
> not use kernel interrupts, does not use kernel DMA, does not use buffer
> cache, does not use any spin locks. Forget about doing I/O during Oops
> unless you can meet these criteria. Serial console does, very little else
> is suitable.

At least the problem with the spin locks can be solved just en passer.
Myself and a few other people are considering solving some of the deadlock
issues that plague especially highly intelligent hardware using lock-free
data structures. These will also provide some key advantages for other
problems we're thinking about.

Ralf

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