Re: [PATCH 1/6] blk-mq: Do not invoke queue operations on a dead queue

[Omar Sandoval <osandov@osandov.com>]

On Fri, Apr 14, 2017 at 04:12:01PM +0000, Bart Van Assche wrote:
> On Fri, 2017-04-14 at 00:40 -0700, Omar Sandoval wrote:
> > On Thu, Apr 13, 2017 at 11:05:32PM +0000, Bart Van Assche wrote:
> > > On Thu, 2017-04-13 at 16:01 -0700, Omar Sandoval wrote:
> > > > Looking at this, I think we have similar issues with most of the other
> > > > debugfs files. Should we move the debugfs cleanup earlier?
> > > 
> > > That's a good question. However, while I was debugging it was very convenient
> > > to be able to access the queue state after it had reached the "dead" state.
> > > Performing the cleanup earlier would be an alternative solution but would
> > > make debugging a bit harder ...
> > 
> > What useful information were you getting out of debugfs once the queue
> > was already dead? Wasn't the interesting stuff freed at that point?
> 
> Hello Omar,
> 
> I'm currently chasing a stall of dm-rq + dm-mpath that occurs after the
> queues below it have reached the "dead" state. I will look for another
> way to obtain the information I need such that we can remove the block
> layer queue debugfs information before these queues reach the "dead"
> state.
> 
> Bart.

Thanks, Bart. In this case, the absence of the "mq" directory should
tell you that the queue is dead. Will you move the cleanup in v2 or
should I submit a separate patch?