diff options
| author | Ming Lei <ming.lei@redhat.com> | 2018-01-17 17:41:52 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-01-17 17:46:27 +0100 |
| commit | 7df938fbc4ee641e70e05002ac67c24b19e86e74 (patch) | |
| tree | 4058ba173eb411422482125e14e7bb12b70c8b38 /block/blk-mq.c | |
| parent | blk-mq: make sure hctx->next_cpu is set correctly (diff) | |
| download | linux-7df938fbc4ee641e70e05002ac67c24b19e86e74.tar.xz linux-7df938fbc4ee641e70e05002ac67c24b19e86e74.zip | |
blk-mq: turn WARN_ON in __blk_mq_run_hw_queue into printk
We know this WARN_ON is harmless and in reality it may be trigged,
so convert it to printk() and dump_stack() to avoid to confusing
people.
Also add comment about two releated races here.
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Stefan Haberland <sth@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "jianchao.wang" <jianchao.w.wang@oracle.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 3bd41f1066ee..ec429be05729 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1294,9 +1294,27 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) /* * 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 */ - WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) && - cpu_online(hctx->next_cpu)); + 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 |