[Bug 52498] New: wineboot does not block main thread

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=52498

Bug ID: 52498
           Summary: wineboot does not block main thread
           Product: Wine
           Version: 7.0
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 71793
  --> https://bugs.winehq.org/attachment.cgi?id=71793
wineboot has non-blocking output

Wine is used as a test tool..

There is a weird behavior when trying to initialize the test env with this
script:

<code>
#! /bin/bash

if ! [ -d "$HOME/.wine" ]; then
  # this prevents wine asking for gecko and mono install
  WINEDLLOVERRIDES="mscoree,mshtml=" wineboot -u
fi
# add some dll paths to the path
wine regedit /opt/add_dll_paths.x86_64-w64-mingw32.shared.posix.reg &>/dev/null
</code>

The weird thing is the regedit process was forked before the wineboot
process had been finished/disappeared.
(regedit can be replaced with any other command)

This causes a very unpredictable wine usage e.g. stuck processes.

Further details in the attachment.

With wine 6.0.2 there was no such an issue.

Environment: 
Ubuntu 18.04 OS 
Running docker container on a focal based Ubuntu image
Wine 7.0