Re: [PATCH 3/3] blk-mq: Fix the queue freezing mechanism

From: Bart Van Assche
Date: Thu Sep 24 2015 - 12:44:01 EST

On 09/23/2015 08:23 PM, Ming Lei wrote:
IMO, mq_freeze_depth should only be accessed in slow path, and looks
the race just happens during the small window between increasing
'mq_freeze_depth' and killing the percpu counter.

Hello Ming,

My concern is that *not* checking mq_freeze_depth in the hot path can cause a livelock. If there is a software layer, e.g. multipathd, that periodically submits new commands and if these commands take time to process e.g. because the transport layer is unavailable, how to guarantee that freezing ever succeeds without checking mq_freeze_depth in the hot path ?


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at