[dm-devel] Re: [RFC PATCH 1/8] rqbased-dm: allow blk_get_request() to be called from interrupt context

[Christoph Hellwig <hch infradead org>]

On Wed, Dec 20, 2006 at 12:50:02PM -0500, Kiyoshi Ueda wrote:
> Because I'd like to use blk_get_request() in q->request_fn()
> which can be called from interrupt context like below:
>   scsi_io_completion -> scsi_end_request -> scsi_next_command
>   -> scsi_run_queue -> blk_run_queue -> q->request_fn

> Or request should not be allocated in q->request_fn() anyway?
> Do you have any other ideas?

The right long-term fix is to make sure request_fn is only ever called
from process context.  This means moving retry handling to a thread instead
of a softirq, but this will need careful performance testing and tweaking.