From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH 04/10] virtio: console: return -ENODEV on all read operations after unplug Date: Fri, 19 Jul 2013 13:07:49 +0800 Message-ID: <51E8C9A5.2070309@redhat.com> References: <39ab201027a58e792724172f1f559fe837e89556.1374177234.git.amit.shah@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <39ab201027a58e792724172f1f559fe837e89556.1374177234.git.amit.shah@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Amit Shah Cc: stable@vger.kernel.org, Virtualization List List-Id: virtualization@lists.linuxfoundation.org On 07/19/2013 04:16 AM, Amit Shah wrote: > If a port gets unplugged while a user is blocked on read(), -ENODEV is > returned. However, subsequent read()s returned 0, indicating there's no > host-side connection (but not indicating the device went away). > > This also happened when a port was unplugged and the user didn't have > any blocking operation pending. If the user didn't monitor the SIGIO > signal, they won't have a chance to find out if the port went away. > > Fix by returning -ENODEV on all read()s after the port gets unplugged. > write() already behaves this way. > > CC: > Signed-off-by: Amit Shah > --- > drivers/char/virtio_console.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > index 6bf0df3..a39702a 100644 > --- a/drivers/char/virtio_console.c > +++ b/drivers/char/virtio_console.c > @@ -749,6 +749,10 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf, > > port = filp->private_data; > > + /* Port is hot-unplugged. */ > + if (!port->guest_connected) > + return -ENODEV; > + What if the port is hot-unplugged after this check? Should we serialize the hot plug with inbuf_lock here? > if (!port_has_data(port)) { > /* > * If nothing's connected on the host just return 0 in > @@ -765,7 +769,7 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf, > if (ret < 0) > return ret; > } > - /* Port got hot-unplugged. */ > + /* Port got hot-unplugged while we were waiting above. */ > if (!port->guest_connected) > return -ENODEV; > /*