Messages in this thread Patch in this message | | | From | Daniel Wagner <> | Subject | [PATCH v2] blk-mq: Remove 'running from the wrong CPU' warning | Date | Mon, 30 Nov 2020 11:19:21 +0100 |
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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> ---
v2: - remove the warning as suggested by Ming v1: - initial version https://lore.kernel.org/linux-block/20201126095152.19151-1-dwagner@suse.de/
block/blk-mq.c | 25 ------------------------- 1 file changed, 25 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 55bcee5dc032..7e6761804f86 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -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. -- 2.16.4
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