On 2020-05-08 19:20, Ming Lei wrote: > Not sure why you mention queue freezing. This patch series introduces a fundamental race between modifying the hardware queue state (BLK_MQ_S_INACTIVE) and tag allocation. The only mechanism I know of for enforcing the order in which another thread observes writes to different memory locations without inserting a memory barrier in the hot path is RCU (see also The RCU-barrier menagerie; https://lwn.net/Articles/573497/). The only existing such mechanism in the blk-mq core I know of is queue freezing. Hence my comment about queue freezing. Thanks, Bart.
