blk-mq: turn WARN_ON in __blk_mq_run_hw_queue into printk
[ Upstream commit 7df938fbc4
]
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>
pull/10/head
parent
2e102fe86e
commit
a1dfcb01e3
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@ -1143,9 +1143,27 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
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/*
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* We should be running this queue from one of the CPUs that
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* are mapped to it.
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*
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* There are at least two related races now between setting
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* hctx->next_cpu from blk_mq_hctx_next_cpu() and running
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* __blk_mq_run_hw_queue():
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*
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* - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
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* but later it becomes online, then this warning is harmless
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* at all
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*
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* - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
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* but later it becomes offline, then the warning can't be
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* triggered, and we depend on blk-mq timeout handler to
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* handle dispatched requests to this hctx
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*/
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WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
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cpu_online(hctx->next_cpu));
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if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
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cpu_online(hctx->next_cpu)) {
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printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
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raw_smp_processor_id(),
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cpumask_empty(hctx->cpumask) ? "inactive": "active");
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dump_stack();
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}
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/*
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* We can't run the queue inline with ints disabled. Ensure that
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