Re: [PATCH 2/2] test/py: Wait for guestmount worker to exit after running guestunmount

[Tom Rini <trini@konsulko.com>]

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On Fri, Jun 04, 2021 at 10:04:46PM +0300, Alper Nebi Yasak wrote:

> Some filesystem tests are failing when their image is prepared with
> guestmount, but succeeding if loop mounts are used instead. The reason
> seems to be a race condition the guestmount(1) manual page explains:
> 
>     When guestunmount(1)/fusermount(1) exits, guestmount may still be
>     running and cleaning up the mountpoint.  The disk image will not be
>     fully finalized.
> 
>     This means that scripts like the following have a nasty race condition:
> 
>      guestmount -a disk.img -i /mnt
>      # copy things into /mnt
>      guestunmount /mnt
>      # immediately try to use 'disk.img' ** UNSAFE **
> 
>     The solution is to use the --pid-file option to write the guestmount
>     PID to a file, then after guestunmount spin waiting for this PID to
>     exit.
> 
> The Python standard library has an os.waitpid() function for waiting a
> child to terminate, but it cannot wait on non-child processes. Implement
> a utility function that can do this by polling the process repeatedly
> for a given duration, optionally killing the process if it won't
> terminate on its own. Apply the suggested solution with this utility
> function, which makes the failing tests succeed again.
> 
> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
> Reviewed-by: Simon Glass <sjg@chromium.org>

Applied to u-boot/master, thanks!

-- 
Tom

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