diff options
| author | Ming Lei <ming.lei@redhat.com> | 2018-01-18 00:41:52 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-26 11:02:07 +0200 |
| commit | a1dfcb01e374729f6920c3c07867914c5e848fb4 (patch) | |
| tree | 37e456b3865f04c7d108dd1e0c347356935559a2 | |
| parent | 2e102fe86ede237ca875da9336648caa5e2fcac6 (diff) | |
blk-mq: turn WARN_ON in __blk_mq_run_hw_queue into printk
[ Upstream commit 7df938fbc4ee641e70e05002ac67c24b19e86e74 ]
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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 6f899669cbdd..007f96611364 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1143,9 +1143,27 @@ 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 |