[PATCH] queue stall with blk-mq-sched

Hi Jens,

I'm trying to debug a queue stall with your blk-mq-sched branch; with my
latest mpt3sas patches fio stops basically directly after starting a
sequential read :-(

I've debugged things and came up with the attached patch; we need to
restart waiters with blk_mq_tag_idle() after completing a tag.
We're already calling blk_mq_tag_busy() when fetching a tag, so I think
calling blk_mq_tag_idle() is required when retiring a tag.

However, even with the attached patch I'm seeing some queue stalls;
looks like they're related to the 'stonewall' statement in fio.

Debugging continues.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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