Re: Correct use of ap->lock versus ap->host->lock ?

[Tejun Heo <htejun@gmail.com>]

Jeff Garzik wrote:
> Jeff Garzik wrote:
>> You need to perform your own LLD-specific locking analysis to see if
>> it is safe to do, e.g. __mv_stop_dma() rather than mv_stop_dma().
> 
> And speaking as the probable author of some of the code that takes a
> lock during EH in sata_mv....   reinforcing that the above quoted
> statement is true.
> 
> Generally I would put in a lock during EH around register or data
> manipulations that were locked elsewhere in the driver, thus
> guaranteeing such code is safe.
> 
> However, it may also be the case that such a lock during EH is
> unnecessary because command submission machinery is disabled.  I chose a
> path that potentially added more locking, but was much easier to verify
> correct.

I think it's generally safe not to grab any locks during resets as all
the submission machinery && the interrupt handler are shut down, so it
should be safe to go lockless.  There may be exceptions tho.

-- 
tejun