Linux Virtualization - Aug 2010 - [PATCH 0/4] virtio: console: fixes, SIGIO

Hi Rusty,

The main thing in these patches is the introduction of injecting SIGIO
on host-side connect/disconnect events and when new data is available
for ports.

The first two patches fix bugs that I haven't seen, but look like the
right thing to do.

These have been tested extensively using the test-virtserial test
suite.

Please apply,
		Amit.

Amit Shah (4):
  virtio: console: Un-block reads on chardev close
  virtio: console: Annotate virtcons_remove with __devexit_p
  virtio: console: Send SIGIO to processes that request it for host
    events
  virtio: console: Send SIGIO on new data arrival on ports

 drivers/char/virtio_console.c |   32 ++++++++++++++++++++++++++++++--
 1 files changed, 30 insertions(+), 2 deletions(-)

-- 
1.7.2.2

If a chardev is closed, any blocked read / poll calls should just return
and not attempt to use other state.

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 942a982..92ae3f8 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -522,6 +522,10 @@ static ssize_t fill_readbuf(struct port *port, char
*out_buf, size_t out_count,
 /* The condition that must be true for polling to end */
 static bool will_read_block(struct port *port)
 {
+	if (!port->guest_connected) {
+		/* Port got hot-unplugged. Let's exit. */
+		return false;
+	}
 	return !port_has_data(port) && port->host_connected;
 }
 
-- 
1.7.2.2

virtcons_remove is called on device unplug. Mark with __devexit_p.

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 92ae3f8..a34f40e 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1585,7 +1585,7 @@ fail:
 	return err;
 }
 
-static void virtcons_remove(struct virtio_device *vdev)
+static void __devexit virtcons_remove(struct virtio_device *vdev)
 {
 	struct ports_device *portdev;
 	struct port *port, *port2;
@@ -1631,7 +1631,7 @@ static struct virtio_driver virtio_console = {
 	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
 	.probe =	virtcons_probe,
-	.remove =	virtcons_remove,
+	.remove =	__devexit_p(virtcons_remove),
 	.config_changed = config_intr,
 };
 
-- 
1.7.2.2

A process can request for SIGIO on host connect / disconnect events
using the O_ASYNC file flag using fcntl().

If that's requested, and if the guest-side connection for the port is
open, any host-side open/close events for that port will raise a SIGIO.
The process can then use poll() within the signal handler to find out
which port triggered the signal.

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index a34f40e..b74d097 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -187,6 +187,9 @@ struct port {
 	/* The 'name' of the port that we expose via sysfs properties */
 	char *name;
 
+	/* We can notify apps of host connect / disconnect events via SIGIO */
+	struct fasync_struct *async_queue;
+
 	/* The 'id' to identify the port with the Host */
 	u32 id;
 
@@ -719,6 +722,14 @@ static int port_fops_open(struct inode *inode, struct file
*filp)
 	return 0;
 }
 
+static int port_fops_fasync(int fd, struct file *filp, int mode)
+{
+	struct port *port;
+
+	port = filp->private_data;
+	return fasync_helper(fd, filp, mode, &port->async_queue);
+}
+
 /*
  * The file operations that we support: programs in the guest can open
  * a console device, read from it, write to it, poll for data and
@@ -732,6 +743,7 @@ static const struct file_operations port_fops = {
 	.write = port_fops_write,
 	.poll  = port_fops_poll,
 	.release = port_fops_release,
+	.fasync = port_fops_fasync,
 };
 
 /*
@@ -1011,6 +1023,7 @@ static int add_port(struct ports_device *portdev, u32 id)
 	port->name = NULL;
 	port->inbuf = NULL;
 	port->cons.hvc = NULL;
+	port->async_queue = NULL;
 
 	port->cons.ws.ws_row = port->cons.ws.ws_col = 0;
 
@@ -1234,6 +1247,13 @@ static void handle_control_message(struct ports_device
*portdev,
 		spin_lock_irq(&port->outvq_lock);
 		reclaim_consumed_buffers(port);
 		spin_unlock_irq(&port->outvq_lock);
+
+		/*
+		 * If the guest is connected, it'll be interested in
+		 * knowing the host connection state changed.
+		 */
+		if (port->async_queue && port->guest_connected)
+			kill_fasync(&port->async_queue, SIGIO, POLL_OUT);
 		break;
 	case VIRTIO_CONSOLE_PORT_NAME:
 		/*
-- 
1.7.2.2

Send a SIGIO signal when new data arrives on a port. This is sent only
when the process has requested for the signal to be sent using fcntl().

Signed-off-by: Amit Shah <amit.shah at redhat.com>
---
 drivers/char/virtio_console.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index b74d097..be0a8e4 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1350,6 +1350,10 @@ static void in_intr(struct virtqueue *vq)
 
 	wake_up_interruptible(&port->waitqueue);
 
+	/* Send a SIGIO indicating new data in case the process asked for it */
+	if (port->async_queue && port->guest_connected)
+		kill_fasync(&port->async_queue, SIGIO, POLL_IN);
+
 	if (is_console_port(port) && hvc_poll(port->cons.hvc))
 		hvc_kick();
 }
-- 
1.7.2.2

On (Thu) Aug 26 2010 [10:34:04], Amit Shah wrote:
> Hi Rusty,
> 
> The main thing in these patches is the introduction of injecting SIGIO
> on host-side connect/disconnect events and when new data is available
> for ports.
> 
> The first two patches fix bugs that I haven't seen, but look like the
> right thing to do.
> 
> These have been tested extensively using the test-virtserial test
> suite.
> 
> Please apply,
Since you haven't picked this up already, I'll send a new series that
has more fixes and another call to SIGIO. I'll also split up the series
in two patchsets, one for hot-unplug related fixes and one for the
SIGIO.

		Amit