| Message ID | 20180226130452.21309-1-dgilbert@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] serial: Open non-block | expand |
On 26/02/2018 14:04, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > 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 <dgilbert@redhat.com> Socket chardevs have "nowait" for that. Should serial have something similar? 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; > } >
* Paolo Bonzini (pbonzini@redhat.com) wrote: > On 26/02/2018 14:04, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > > > 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 <dgilbert@redhat.com> > > 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 / dgilbert@redhat.com / Manchester, UK
On 26/02/2018 14:04, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > 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 <dgilbert@redhat.com> > --- > 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; > } > Queued, thanks. Paolo
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; }