Re: [PATCH v2 14/15] block: Don't poll in bdrv_replace_child_noperm()

[Kevin Wolf <kwolf@redhat.com>]

Am 09.12.2022 um 17:53 hat Paolo Bonzini geschrieben:
> On 11/18/22 18:41, Kevin Wolf wrote:
> > In order to make sure that bdrv_replace_child_noperm() doesn't have to
> > poll any more, get rid of the bdrv_parent_drained_begin_single() call.
> > 
> > This is possible now because we can require that the parent is already
> > drained through the child in question when the function is called and we
> > don't call the parent drain callbacks more than once.
> > 
> > The additional drain calls needed in callers cause the test case to run
> > its code in the drain handler too early (bdrv_attach_child() drains
> > now), so modify it to only enable the code after the test setup has
> > completed.
> > 
> > Signed-off-by: Kevin Wolf<kwolf@redhat.com>
> 
> I hate to bear bad news, but this breaks the Windows builds on github
> (msys-32bit, msys-64bit) with an obscure but 100% reproducible
> 
> 51/88 qemu:unit / test-bdrv-drain ERROR           1.30s   (exit status
> 3221225477 or signal 3221225349 SIGinvalid)
> 
> The exit status is 0xC0000005 aka a Windows SIGSEGV.  With some luck it
> could be reproducible with Wine (but no gdb).

I can reproduce it with mingw+wine (and actually gdb! Still a somewhat
limited debugging environment, but not as bad as I imagined.)

I looks to me like this is a problem with the test case rather than the
change per se. It seems to be fixed with this patch that is already
posted as part of the next series:

[PATCH 09/18] test-bdrv-drain: Fix incorrrect drain assumptions
https://lists.gnu.org/archive/html/qemu-block/2022-12/msg00165.html

Kevin