Hi Linus,
We've had an issue with scsi-mq where probing takes forever. This was
bisected down to the percpu changes for blk_mq_queue_enter(), and the
fact we now suffer an RCU grace period when killing a queue. SCSI
creates and destroys tons of queues, so this let to 10s of seconds of
stalls at boot for some.
Tejun has a real fix for this, but it's too involved for 3.17. So this
is a temporary workaround to expedite the queue killing until we can
fold in the real fix for 3.18 when that merge window opens.
Please pull!
git://git.kernel.dk/linux-block.git for-linus
for you to fetch changes up to 0a30288da1aec914e158c2d7a3482a85f632750f:
blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe
(2014-09-24 08:29:36 -0600)
----------------------------------------------------------------
Tejun Heo (1):
blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe
block/blk-mq.c | 11 ++++++++++-
include/linux/percpu-refcount.h | 1 +
lib/percpu-refcount.c | 16 ++++++++++++++++
3 files changed, 27 insertions(+), 1 deletion(-)
--
Jens Axboe
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