blk-mq: Remove 'running from the wrong CPU' warning (e6582cb5) · Commits · 戴 / test

It's guaranteed that no request is in flight when a hctx is going offline. This warning is only triggered when the wq's CPU is hot plugged and the blk-mq is not synced up yet. As this state is temporary and the request is still processed correctly, better remove the warning as this is the fast path. Suggested-by:

Ming Lei <ming.lei@redhat.com> Signed-off-by:

Daniel Wagner <dwagner@suse.de> Reviewed-by:

Christoph Hellwig <hch@lst.de> Reviewed-by:

Ming Lei <ming.lei@redhat.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

+0 −25

Original line number	Diff line number	Diff line
		@@ -1495,31 +1495,6 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
		{
		int srcu_idx;

		/*
		* We should be running this queue from one of the CPUs that
		* are mapped to it.
		*
		* There are at least two related races now between setting
		* hctx->next_cpu from blk_mq_hctx_next_cpu() and running
		* __blk_mq_run_hw_queue():
		*
		* - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
		* but later it becomes online, then this warning is harmless
		* at all
		*
		* - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
		* but later it becomes offline, then the warning can't be
		* triggered, and we depend on blk-mq timeout handler to
		* handle dispatched requests to this hctx
		*/
		if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
		cpu_online(hctx->next_cpu)) {
		printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
		raw_smp_processor_id(),
		cpumask_empty(hctx->cpumask) ? "inactive": "active");
		dump_stack();
		}

		/*
		* We can't run the queue inline with ints disabled. Ensure that
		* we catch bad users of this early.

Admin message