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 <[email protected]> --- drivers/char/virtio_console.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 66875d6..3a305f8 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -168,6 +168,9 @@ 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. */ @@ -471,6 +474,8 @@ 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; } @@ -489,6 +494,15 @@ 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->readbuf_list_lock); + if (port->guest_connected) { + spin_unlock_irq(&port->readbuf_list_lock); + return -EMFILE; + } + port->guest_connected = true; + spin_unlock_irq(&port->readbuf_list_lock); + /* Notify host of port being opened */ send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1); @@ -656,6 +670,7 @@ 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; return 0; } -- 1.6.2.5 _______________________________________________ Virtualization mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/virtualization
