Re: [PATCH 3/9] scsi: improved eh timeout handler

[Bart Van Assche <bvanassche@acm.org>]

On 06/11/13 20:57, James Bottomley wrote:
> Actually, I think we can dump the workqueue altogether.  The only reason
> we need it is because the current abort handlers wait for the command
> and return the completion state.  However, all LLDs are capable of
> emitting TMFs at interrupt level, so if we separated the emit from the
> wait, we could simply do this sequence:
>
> on timeout, fire the abort from interrupt and mark the command as having
> an abort issued (possibly by adding a pointer to the abort task), return
> BLK_EH_RESET_TIMER.
>
> Now if the timeout fires again, assume the abort was unsuccessful and
> escalate to LUN reset.
>
> This is fully asynchronous, fully tracked and doesn't rely on work
> queues.
>
> The necessary additions for something like this are the from interrupt
> issue abort and LUN reset, which could just be additional callbacks in
> the host template.

Do we really need a new callback in the host template for a command 
abort that does not wait ? Several LLDs already have their own internal 
data structures for keeping track of the request state and can use these 
data structures to set a flag "command has been aborted". If aborting a 
command fails and the command completes that flag can then be used to 
avoid a second invocation of scsi_done(). At least, that's what the SRP 
initiator already does today in srp_abort().

Bart.