Re: [Qemu-devel] [Qemu-block] [PATCH 6/7] qemu-iotests: 141: reduce likelihood of race condition on systems with fast IO

[Max Reitz <mreitz@redhat.com>]

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On 05.04.2016 11:21, Sascha Silbe wrote:
> On systems with fast IO, qemu-io may write more than 1 MiB before
> receiving the block-job-cancel command, causing the test case to fail.
> 
> 141 is inherently racy, but we can at least reduce the likelihood of the
> job completing before the cancel command arrives by bumping the size of
> the data getting written; we'll try 32 MiB for a start.

Hm, interesting. I tried to prevent this by setting the block jobs'
speed to 1, which should make it stop after the block job has processed
the first block of data.

I won't oppose this patch, because if it fixes things for you, that's
good. But I don't think it should be necessary.

Max

> 
> Once we actually move enough data around for the block job not to
> complete prematurely, the test will still fail because the offset value
> in the BLOCK_JOB_CANCELLED event will vary. Since this is more or less
> inherent to the nature of this event, we just replace it with a fixed
> value globally (in _filter_qmp), the same way we handle timestamps.
> 
> Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
> Reviewed-by: Bo Tu <tubo@linux.vnet.ibm.com>
> ---
>  tests/qemu-iotests/141           | 11 ++++++-----
>  tests/qemu-iotests/141.out       | 24 ++++++++++++------------
>  tests/qemu-iotests/common.filter |  1 +
>  3 files changed, 19 insertions(+), 17 deletions(-)


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