Messages in this thread | | | Date | Mon, 5 Jul 2021 18:34:00 +0200 | From | Daniel Wagner <> | Subject | Re: [PATCH 2/2] nvme-fc: Wait with a timeout for queue to freeze |
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On Tue, Jun 29, 2021 at 09:39:30AM +0800, Ming Lei wrote: > Can you investigate a bit on why there is the hang? FC shouldn't use > managed IRQ, so the interrupt won't be shutdown.
So far, I was not able to figure out why this hangs. In my test setup I don't have to do any I/O, I just toggle the remote port.
grep busy /sys/kernel/debug/block/*/hctx*/tags | grep -v busy=0
and this seems to confirm, no I/O in flight.
So I started to look at the q_usage_counter. The obvious observational is that counter is not 0. The least bit is set, thus we are in atomic mode.
(gdb) p/x *((struct request_queue*)0xffff8ac992fbef20)->q_usage_counter->data $10 = { count = { counter = 0x8000000000000001 }, release = 0xffffffffa02e78b0, confirm_switch = 0x0, force_atomic = 0x0, allow_reinit = 0x1, rcu = { next = 0x0, func = 0x0 }, ref = 0xffff8ac992fbef30 }
I am a bit confused about the percpu-refcount API. My naive interpretation is that when we are in atomic mode percpu_ref_is_zero() can't be used. But this seems rather strange. I must miss something.
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