Re: INFO: task hung in sync_blockdev

[Dmitry Vyukov]

On Thu, Feb 8, 2018 at 5:23 PM, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote:
>
>
> On 02/08/2018 07:18 PM, Jan Kara wrote:
>
>>> By "full kernel crashdump" you mean kdump thing, or something else?
>>
>> Yes, the kdump thing (for KVM guest you can grab the memory dump also from
>> the host in a simplier way and it should be usable with the crash utility
>> AFAIK).
>>
>
> In QEMU monitor 'dump-guest-memory' command:
>
> (qemu) help dump-guest-memory
> dump-guest-memory [-p] [-d] [-z|-l|-s] filename [begin length] -- dump guest memory into file 'filename'.
>                         -p: do paging to get guest's memory mapping.
>                         -d: return immediately (do not wait for completion).
>                         -z: dump in kdump-compressed format, with zlib compression.
>                         -l: dump in kdump-compressed format, with lzo compression.
>                         -s: dump in kdump-compressed format, with snappy compression.
>                         begin: the starting physical address.
>                         length: the memory size, in bytes


Nice!
Do you know straight away if it's scriptable/automatable? Or do I just
send some magic sequence of bytes representing ^A+C,
dump-guest-memory, \n to stdin pipe?

Unfortunately, syzbot uses GCE VMs for testing, and there does not
seem to be such feature on GCE...