Re: [PATCH v4 00/15] Reverse debugging

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

On 21.09.2020 09:03, Pavel Dovgalyuk wrote:
> On 20.09.2020 10:58, Paolo Bonzini wrote:
>> On 14/09/20 08:06, Pavel Dovgalyuk wrote:
>>> GDB remote protocol supports reverse debugging of the targets.
>>> It includes 'reverse step' and 'reverse continue' operations.
>>> The first one finds the previous step of the execution,
>>> and the second one is intended to stop at the last breakpoint that
>>> would happen when the program is executed normally.
>>>
>>> Reverse debugging is possible in the replay mode, when at least
>>> one snapshot was created at the record or replay phase.
>>> QEMU can use these snapshots for travelling back in time with GDB.
>>
>> I had queued this, it is a very nice patch series.  Unfortunately, the
>> tests failed on gitlab:
>>
>> https://gitlab.com/bonzini/qemu/-/jobs/745795080
> 
> There is a strange thing in your environment:
> 
> 15:49:41 INFO | Downloading/preparing boot image
> 15:49:42 INFO | Running '/builds/bonzini/qemu/build/qemu-img create -f 
> qcow2 -b 
> /builds/bonzini/qemu/avocado-cache/by_location/d2a8d6b607afec50de14560c064f34ffd99836b2/Fedora-Cloud-Base-31-1.9.x86_64.qcow2 
> /var/tmp/avocado_tj2janfx/avocado_job_ys7ueohj/04-tests_acceptance_boot_linux.py_BootLinuxX8664.test_pc_q35_kvm/Fedora-Cloud-Base-31-1.9.x86_64-d1ac1224.qcow2' 
> 
> 
> 
> It downloads boot image, but there is no such requirement in the test.
> And all this stuff consumes most of the time for the test.

Sorry, that was ok. It was the output from the previous test.

For reverse debugging there was a timeout on reading from the socket: 
result = self._socket.recv(REMOTE_MAX_PACKET_SIZE)

Do you have any hint how to debug such a failure in this environment?

Pavel Dovgalyuk