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virtio: console: Ensure only one process can have a port open at a time 

Add a guest_connected field that ensures only one process
can have a port open at a time.

This also ensures we don't have a race when we later add support for
dropping buffers when closing the char dev and buffer caching is turned
off for the particular port.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Amit Shah 2009-11-26 11:25:38 +05:30 committed by Rusty Russell
parent 2030fa496d
commit 3c7969ccb5
1 changed files with 17 additions and 1 deletions
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18
drivers/char/virtio_console.c
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@ -175,6 +175,9 @@ struct port {
/* Is the host device open */
bool host_connected;
/* We should allow only one process to open a port */
bool guest_connected;
};
/* This is the very early arch-specified put chars function. */
@ -528,6 +531,8 @@ static int port_fops_release(struct inode *inode, struct file *filp)
/* Notify host of port being closed */
send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
port->guest_connected = false;
return 0;
}
@ -546,6 +551,16 @@ static int port_fops_open(struct inode *inode, struct file *filp)
if (is_console_port(port))
return -ENXIO;
/* Allow only one process to open a particular port at a time */
spin_lock_irq(&port->inbuf_lock);
if (port->guest_connected) {
spin_unlock_irq(&port->inbuf_lock);
return -EMFILE;
}
port->guest_connected = true;
spin_unlock_irq(&port->inbuf_lock);
/* Notify host of port being opened */
send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
@ -709,6 +724,7 @@ int init_port_console(struct port *port)
pdrvdata.next_vtermno++;
list_add_tail(&port->cons.list, &pdrvdata.consoles);
spin_unlock_irq(&pdrvdata_lock);
port->guest_connected = true;
/* Notify host of port being opened */
send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
@ -856,7 +872,7 @@ static int add_port(struct ports_device *portdev, u32 id)
port->inbuf = NULL;
port->cons.hvc = NULL;
port->host_connected = false;
port->host_connected = port->guest_connected = false;
port->in_vq = portdev->in_vqs[port->id];
port->out_vq = portdev->out_vqs[port->id];