Re: [PATCH v4 0/7] blk-mq: fix race conditions on cpu hotplug handling

From: Jens Axboe
Date: Tue Sep 29 2015 - 13:32:08 EST

On 09/26/2015 11:09 AM, Akinobu Mita wrote:
This patchset addresses several race conditions on cpu hotplug handling
for blk-mq. All problems can be reproducible by the following script.

while true; do
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
done &

while true; do
modprobe -r null_blk
modprobe null_blk queue_mode=2 irqmode=1
sleep 0.1

* Changes from v3
- Rebased to the latest kernel
- Add Reviewed-by tags

I've reviewed the patches, looks good to me. I've skipped 6/7, as I think we should fix that as part of the percpu ref counting, and not handle it specifically in blk-mq. If we can't get that fix before 4.3 wraps up, then we can revisit and put that in as well.


Jens Axboe

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