Messages in this thread | | | Date | Tue, 6 Jul 2021 15:29:11 +0800 | From | Ming Lei <> | Subject | Re: [PATCH 2/2] nvme-fc: Wait with a timeout for queue to freeze |
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On Mon, Jul 05, 2021 at 06:34:00PM +0200, Daniel Wagner wrote: > 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.
What is the output of the following command after the hang is triggered?
(cd /sys/kernel/debug/block/nvme0n1 && find . -type f -exec grep -aH . {} \;)
Suppose the hang disk is nvme0n1.
> > 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.
No, percpu_ref_is_zero() is fine to be called in atomic mode.
Thanks, Ming
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