Re: [patch 1/16] unplugging fix

[Jens Axboe]

On Sun, Jun 02 2002, Andrew Morton wrote:
> Andrew Morton wrote:
> > 
> > There's a plugging bug in 2.5.19.  Once you start pushing several disks
> > hard, the new unplug code gets confused and queues are left in plugged
> > state, but not on the plug list.  They never get unplugged and the
> > machine dies mysteriously.
> > 
> 
> This patch didn't fix it.  It made it tons better, but I again have a
> wedged box.  Same symptoms - against IDE this time.
> 
> blk_plug_list is empty.  queue_flags=0x03.  Interestingly,
> q->plug_list is non-empty, non-zero, both list members pointing at
> a list which isn't either itself or blk_plug_list.
> 
> I note that the code isn't taking queues off the plug list when the queue
> is destroyed.  Guess that doesn't matter - we never destroy a plugged
> queue...
> 
> This one is killing me.

I've got a good handle on how to clean the whole plugging thing up, I
suspect it will make this case easier to fix. I'll be back with that
tomorrow, still got guests...

-- 
Jens Axboe