We found a race in the block message queue for kernel v5.18-rc5 using
a race testing tool we are developing. We are reporting this race
because it appears to be potentially harmful. The race occurs in
block/blk-mq-sched.c:333 blk_mq_sched_dispatch_requests
hctx->run++;
where multiple threads can schedule dispatch requests and increment
the request counter htctx->run simultaneously. This appears to lead to
undefined behavior where multiple conflicting updates to the hctx->run
value could result in it not matching the number of requests that
have been scheduled with calls to blk_mq_sched_dispatch_requests.
Best,
Gabe
