Re: [Qemu-block] [Qemu-devel] [PATCH] iotests: Fix 219's timing

[Peter Maydell]

On 6 June 2018 at 19:37, Max Reitz <address@hidden> wrote:
> 219 has two issues that may lead to sporadic failure, both of which are
> the result of issuing query-jobs too early after a job has been
> modified.  This can then lead to different results based on whether the
> modification has taken effect already or not.
>
> First, query-jobs is issued right after the job has been created.
> Besides its current progress possibly being in any random state (which
> has already been taken care of), its total progress too is basically
> arbitrary, because the job may not yet have been able to determine it.
> This patch addresses this by just filtering the total progress, like
> what has been done for the current progress already.  However, for more
> clarity, the filtering is changed to replace the values by a string
> 'FILTERED' instead of deleting them.
>
> Secondly, query-jobs is issued right after a job has been resumed.  The
> job may or may not yet have had the time to actually perform any I/O,
> and thus its current progress may or may not have advanced.  To make
> sure it has indeed advanced (which is what the reference output already
> assumes), insert a sleep of 100 ms before query-jobs is invoked.  With a
> slice time of 100 ms, a buffer size of 64 kB and a speed of 256 kB/s,
> this should be the right amount of time to let the job advance by
> exactly 64 kB.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
> v2: Changed the query-jobs progress filtering [Eric]
> ---

I know nothing about the iotests, so this might be off-base,
but this looks rather like "try to fix a race condition by
adding a sleep", which generally doesn't work very well ?

thanks
-- PMM