Re: [PATCH] sg: fix q->queue_lock on scsi_error_handler path

[Douglas Gilbert <dgilbert@interlog.com>]

FUJITA Tomonori wrote:
> This is a fix for another fallout of the block layer conversion (sorry
> again).
> 
> This should be go into 2.6.28.y and 2.6.29.y.
> 
> However, this should go with patches that I sent for 2.6.29.1 and
> were dropped. So I don't use 'stable@kernel.org' tag.
> 
> =
> From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Subject: [PATCH] [PATCH] sg: fix q->queue_lock on scsi_error_handler path
> 
> sg_rq_end_io() is called via rq->end_io. In some rare cases,
> sg_rq_end_io calls blk_put_request/blk_rq_unmap_user (when a program
> issuing a command has gone before the command completion; e.g. by
> interrupting a program issuing a command before the command
> completes).
> 
> We can't call blk_put_request/blk_rq_unmap_user in interrupt so the
> commit c96952ed7031e7c576ecf90cf95b8ec099d5295a uses
> execute_in_process_context().
> 
> The problem is that scsi_error_handler() calls rq->end_io too. We
> can't call blk_put_request/blk_rq_unmap_user too in this path (we hold
> q->queue_lock).
> 
> To avoid the above problem, in these rare cases, this patch always
> uses schedule_work() instead of execute_in_process_context().
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>