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From: Thomas Huth <thuth@redhat.com>
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Date: Thu, 18 Oct 2018 14:38:01 +0200
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Subject: Re: [Qemu-devel] [PULL 2/7] tests/migration: Enable the migration
 test on s390x, too
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To: "Emilio G. Cota" <cota@braap.org>, "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, quintela@redhat.com, wei@redhat.com, i.maximets@samsung.com, den@openvz.org, Peter Maydell <peter.maydell@linaro.org>

On 2018-10-17 21:28, Emilio G. Cota wrote:
> On Thu, Oct 11, 2018 at 20:25:08 +0100, Dr. David Alan Gilbert (git) wr=
ote:
>> From: Thomas Huth <thuth@redhat.com>
>>
>> We can re-use the s390-ccw bios code to implement a small firmware
>> for a s390x guest which prints out the "A" and "B" characters and
>> modifies the memory, as required for the migration test.
>>
>> [quintela: Converted the compile script to Makefile rules]
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> Message-Id: <1539078677-25396-1-git-send-email-thuth@redhat.com>
>> Reviewed-by: Philippe Mathieu-Daud=C3=A9 <philmd@redhat.com>
>> Tested-by: Philippe Mathieu-Daud=C3=A9 <philmd@redhat.com>
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>   Fixed up Makefile since the aarch patch sneaked in first
>=20
> I suspect this test is giving me intermittent hangs. I've seen the hang=
s
> in different machines, but when they're lightly loaded the
> hang happens more frequently.
>=20
> To reproduce:
>=20
> $ ./configure --target-list=3Ds390x-softmmu
> $ make clean && make
> $ for i in $(seq 0 150); do echo $i && make -j check-qtest || break; do=
ne
>=20
> It usually ends up hanging before 50 runs. When the hang happens, I see
> two qemu-system-s390x processes with:
>=20
> -serial file:/tmp/migration-test-0FZErQ/dest_serial
>=20
> as an argument, among others. That means the migration test is the
> one hanging, correct?
>=20
> Attaching with gdb just shows the TCG thread waiting for work
> in qemu_tcg_rr_wait_io_event.
>=20
> Can anyone reproduce this? Otherwise, let me know what other info
> I could provide.

I've finally been able to reproduce it - seems like it only happens here
when the host is under heavy load.

... not sure whether I've got time to debug this before KVM forum, so if
it bugs you, feel free to send a patch to disable the test in
tests/Makefile.include for s390x again.

 Thomas