Re: [RFC][PATCH] add blockconsole

[Jeff Moyer]

JÃrn Engel <joern@xxxxxxxxx> writes:

> On Wed, 25 April 2012 09:42:39 -0400, Jeff Moyer wrote:
>> 
>> Neat idea, but I'm curious to know how it works when the system panics
>> and you no longer can schedule the writeback thread.  What are the
>> limitations you've seen in practice?
>
> If the writeback thread doesn't get scheduled, you lose that
> information.  Formerly I did the submit_bio directly, but lockdep
> reminded me that I shouldn't do so from interrupt context.  Bummer.

Well, submit_bio can sleep, obviously.  Perhaps you could explore
registering a panic notifier, and then flush the logs from there?
Unfortunately, there is always the possibility that some required locks
will be taken, but it might get you a little bit further.  Or, you could
explore the route that the diskdump or lkcd folks took, implementing
their own polling mode drivers.

Cheers,
Jeff
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