aboutsummaryrefslogtreecommitdiffstats
path: root/block
diff options
context:
space:
mode:
authorMing Lei <ming.lei@redhat.com>2018-01-18 00:41:52 +0800
committerJens Axboe <axboe@kernel.dk>2018-01-17 09:46:27 -0700
commit7df938fbc4ee641e70e05002ac67c24b19e86e74 (patch)
tree4058ba173eb411422482125e14e7bb12b70c8b38 /block
parent7bed45954b95601230ebf387d3e4e20e4a3cc025 (diff)
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')
-rw-r--r--block/blk-mq.c22
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

Privacy Policy