Hi On Tue, Sep 20, 2022 at 2:33 PM Bin Meng <bmeng...@gmail.com> wrote:
> From: Xuzhou Cheng <xuzhou.ch...@windriver.com> > > The combination of GENERIC_WRITE and FILE_SHARE_READ options does > not allow the same file to be opened again by CreateFile() from > another QEMU process with the same options when the previous QEMU > process still holds the file handle opened. > > This was triggered by running the test_multifd_tcp_cancel() case on > Windows, which cancels the migration, and launches another QEMU > process to migrate with the same file opened for write. Chances are > that the previous QEMU process does not quit before the new QEMU > process runs hence the old one still holds the file handle that does > not allow shared write permission then the new QEMU process will fail. > > As per [1] we should add FILE_SHARE_WRITE to the share mode to allow > such use case. This change makes the behavior be consistent with the > POSIX platforms. > > [1] > https://docs.microsoft.com/en-us/windows/win32/fileio/creating-and-opening-files > > Signed-off-by: Xuzhou Cheng <xuzhou.ch...@windriver.com> > Signed-off-by: Bin Meng <bin.m...@windriver.com> > --- > > Changes in v2: > - Update commit message to include the use case why we should set > FILE_SHARE_WRITE when openning the file for win32 > As discussed in v1, I would rather leave that patch out of this series, since the visible issue is solved differently elsewhere. Also, I disagree with the approach to make windows behaviour consistent with posix here, since I consider the windows behaviour (exclusive write access) superior. I would rather teach the posix implementation about exclusive write access. > chardev/char-file.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/chardev/char-file.c b/chardev/char-file.c > index 2fd80707e5..66385211eb 100644 > --- a/chardev/char-file.c > +++ b/chardev/char-file.c > @@ -60,8 +60,8 @@ static void qmp_chardev_open_file(Chardev *chr, > flags = CREATE_ALWAYS; > } > > - out = CreateFile(file->out, accessmode, FILE_SHARE_READ, NULL, flags, > - FILE_ATTRIBUTE_NORMAL, NULL); > + out = CreateFile(file->out, accessmode, FILE_SHARE_READ | > FILE_SHARE_WRITE, > + NULL, flags, FILE_ATTRIBUTE_NORMAL, NULL); > if (out == INVALID_HANDLE_VALUE) { > error_setg(errp, "open %s failed", file->out); > return; > -- > 2.34.1 > > > -- Marc-André Lureau
