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Re: [Qemu-devel] [PATCH 1/1] serial: Open non-block
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 1/1] serial: Open non-block |
Date: |
Mon, 26 Feb 2018 15:13:29 +0000 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
* Paolo Bonzini (address@hidden) wrote:
> On 26/02/2018 14:04, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > On a real serial device, the open can block if the handshake
> > lines are in a particular state. If a QEMU is passing the serial
> > device to the guest, the QEMU startup is blocked opening the device
> > (with a symptom seen as a timeout from libvirt).
> >
> > Open the serial port with O_NONBLOCK.
> >
> > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
>
> Socket chardevs have "nowait" for that. Should serial have something
> similar?
Hmm, maybe, although I think for real serial the nonblocking open should
be the default.
I've not got any more complex tests though for it.
stty -F uses the same trick of opening non-blocking.
Dave
> Thanks,
>
> Paolo
>
> > ---
> > chardev/char-serial.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/chardev/char-serial.c b/chardev/char-serial.c
> > index feb52e559d..97be5d4a63 100644
> > --- a/chardev/char-serial.c
> > +++ b/chardev/char-serial.c
> > @@ -265,7 +265,8 @@ static void qmp_chardev_open_serial(Chardev *chr,
> > ChardevHostdev *serial = backend->u.serial.data;
> > int fd;
> >
> > - fd = qmp_chardev_open_file_source(serial->device, O_RDWR, errp);
> > + fd = qmp_chardev_open_file_source(serial->device, O_RDWR | O_NONBLOCK,
> > + errp);
> > if (fd < 0) {
> > return;
> > }
> >
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK