On Mon, May 10, 2021 at 10:59:39AM +0200, Emanuele Giuseppe Esposito wrote:
> Progressmeter is protected by the AioContext mutex, which
> is taken by the block jobs and their caller (like blockdev).
> 
> We would like to remove the dependency of block layer code on the
> AioContext mutex, since most drivers and the core I/O code are already
> not relying on it.
> 
> The simplest thing to do is to add a mutex to be able to provide
> an accurate snapshot of the progress values to the caller.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
>  blockjob.c                    | 33 +++++++++++++++++++++++++--------
>  include/qemu/progress_meter.h | 31 +++++++++++++++++++++++++++++++
>  job-qmp.c                     |  8 ++++++--
>  job.c                         |  3 +++
>  qemu-img.c                    |  9 ++++++---
>  5 files changed, 71 insertions(+), 13 deletions(-)

Unlike the next two patches where I had comments, here adding the lock
makes sense to me - the point of the progress meter is to report numbers
to the monitor thread so thread-safety is a key part of the API's value.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>