Re: [PATCH] Fix aic7xxx del_timer_sync() deadlock

[Jeff Garzik <jgarzik@pobox.com>]

Jens Axboe wrote:
> On Sun, Feb 29 2004, Jeff Garzik wrote:
>>If you call blk_start_queue() from io completion -- as you should -- 
>>then it gets called unconditionally, regardless of whether there is IO 
>>pending or not.  The LLD should only care if it can accept more 
>>requests.  The opportunity seems to be there, to me...
> 
> 
> You are still assuming you have io pending when you call
> blk_stop_queue(). If some condition prevents you from queueing the first
> request, you call blk_stop_queue() without having anything to start the
> queue again.

ok, I got it.  I thought your "io pending" was referring to requests in 
the request_queue, not requests active in the LLD.

Still, this is the responsibility of the LLD, right?  For example, 
before any requests are ever sent to the request_queue, the LLD may 
choose to call blk_stop_queue() to prevent queueing while it probes or 
resets the bus.  That would be a case where there is no io pending, for 
both definitions of the phrase :)  And it would be up to the LLD to call 
blk_start_queue() again.  Right?

	Jeff