[dm-devel] blk-mq request allocation stalls [was: Re: [PATCH v3 0/8] dm: add request-based blk-mq support]

[Mike Snitzer]

On Fri, Jan 09 2015 at  4:11pm -0500,
Jens Axboe <axboe at kernel.dk> wrote:

> 
> Actually, try this one instead, it should be a bit more precise than
> the first.
> 

Thanks for the test patch.

I'm still seeing failures that look wrong (last_tag=127 could be edge
condition not handled properly?):

[   14.254632] __bt_get: values before for loop: last_tag=127, index=3
[   14.255841] __bt_get: values after  for loop: last_tag=64, index=2
[   14.257036]
[   14.257036] bt_get: __bt_get() returned -1
[   14.258051] queue_num=0, nr_tags=128, reserved_tags=0, bits_per_word=5
[   14.259246] nr_free=128, nr_reserved=0
[   14.259963] active_queues=0

[  213.115997] __bt_get: values before for loop: last_tag=127, index=3
[  213.117115] __bt_get: values after  for loop: last_tag=96, index=3
[  213.118200]
[  213.118200] bt_get: __bt_get() returned -1
[  213.121593] queue_num=0, nr_tags=128, reserved_tags=0, bits_per_word=5
[  213.123960] nr_free=128, nr_reserved=0
[  213.125880] active_queues=0

[  239.158079] __bt_get: values before for loop: last_tag=8, index=0
[  239.160363] __bt_get: values after  for loop: last_tag=0, index=0
[  239.162896]
[  239.162896] bt_get: __bt_get() returned -1
[  239.166284] queue_num=0, nr_tags=128, reserved_tags=0, bits_per_word=5
[  239.168623] nr_free=127, nr_reserved=0
[  239.170508] active_queues=0