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

From: Akinobu Mita
Date: Sat Sep 26 2015 - 13:09:56 EST

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

* Changes from v2
- Add regression fix for hctx->tags->cpumask
- Remove BLK_MQ_F_SYSFS_UP per-hctx flag and use mq_sysfs_init_done
per-queue flag instead with appropriate locking in order to keep
track of 'mq' sysfs entry's life
- Add comments on non-trivial stuffs, suggested by Ming

* Changes from v1
- Release q->mq_map in blk_mq_release()
- Fix deadlock when reading cpu_list
- Fix race freeze and unfreeze

Akinobu Mita (7):
blk-mq: avoid setting hctx->tags->cpumask before allocation
blk-mq: fix sysfs registration/unregistration race
blk-mq: Fix use after of free q->mq_map
blk-mq: fix q->mq_usage_counter access race
blk-mq: avoid inserting requests before establishing new mapping
blk-mq: fix freeze queue race
blk-mq: fix deadlock when reading cpu_list

block/blk-core.c | 1 +
block/blk-mq-cpumap.c | 9 +++--
block/blk-mq-sysfs.c | 36 ++++++++++++------
block/blk-mq.c | 100 +++++++++++++++++++++++++++++++++++++------------
block/blk-mq.h | 3 +-
include/linux/blk-mq.h | 1 -
include/linux/blkdev.h | 8 ++++
7 files changed, 116 insertions(+), 42 deletions(-)

Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Ming Lei <tom.leiming@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/