Messages in this thread | | | Subject | Re: [PATCH] nvme-pci: use NOWAIT flag for nvme_set_host_mem | From | "jianchao.wang" <> | Date | Mon, 29 Jan 2018 16:06:13 +0800 |
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On 01/29/2018 11:07 AM, Jianchao Wang wrote: > nvme_set_host_mem will invoke nvme_alloc_request without NOWAIT > flag, it is unsafe for nvme_dev_disable. The adminq driver tags > may have been used up when the previous outstanding adminq requests > cannot be completed due to some hardware error. We have to depend > on the timeout path to complete the previous outstanding adminq > requests and free the tags. > However, nvme_timeout will invoke nvme_dev_disable and try to > get the shutdown_lock which is held by another context who is > sleeping to wait for the tags to be freed by timeout path. A > deadlock comes up. > > To fix it, let nvme_set_host_mem use NOWAIT flag.
In fact, this is the only case about nvme_set_host_mem in nvme_dev_disable. Consider the following case:
A adminq request expired.
timeout_work context nvme_timeout -> nvme_dev_disable -> nvme_set_host_mem if this adminq request expires again, the timeout_work cannot handle this case, because it is waiting for the result of nvme_set_host_mem.
Thanks Jianchao
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