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Date:      Mon, 10 Aug 2020 13:04:35 +0200
From:      Hans Petter Selasky <hps@selasky.org>
To:        Alexandre Levy <a13xlevy@gmail.com>
Cc:        freebsd-current@freebsd.org
Subject:   Re: Kernel crash during video transcoding
Message-ID:  <51a2fe4f-5a3e-8d24-19e2-3cdaa8378015@selasky.org>
In-Reply-To: <CAEWSB33_ka2aQb81UmODu72Be_9Vvqi4Qb-jfXHEZ1HgCqwADQ@mail.gmail.com>
References:  <CAEWSB323c2zapSG30OS5T30Wd_bpT=7NbvrPtsyQDRRHQUf7qA@mail.gmail.com> <13793020-1bde-b13f-65e3-909e27d876ad@selasky.org> <CAEWSB323KtVrixgRyKsekdgcGjFm4kUqG6qDE59Aev3Cc6sYBg@mail.gmail.com> <4e9d9a89-4883-1f1c-c796-e5925fd171cc@selasky.org> <CAEWSB30YNwQ7Bpv00P-B=TTHCqT_aFm30552n51Pic1uN5hnZQ@mail.gmail.com> <CAEWSB33_ka2aQb81UmODu72Be_9Vvqi4Qb-jfXHEZ1HgCqwADQ@mail.gmail.com>

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Hi,

On 2020-08-10 12:59, Alexandre Levy wrote:
> Looking at the code, the error happens during the call to VM_OBJECT_WLOCK
> (memory page locking for write ?) in the intel_freebsd.c (see [1] below).
> I'm out for a few days but I'll try to dig more into it when I'm back next
> weekend although I have no experience in the drm-devel-kmod codebase. In
> the meantime if you have any suggestions on debugging this further I'm
> happy to follow them.

The problem is likely that the vm_obj is NULL.

I think I recall that this function is special and can only be called 
from a certain context, unlike in Linux. Will need the full backtrace 
with line numbers in order to debug this.

--HPS



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