diff options
| -rw-r--r-- | drivers/char/virtio_console.c | 80 |
1 files changed, 64 insertions, 16 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 8a9c140d19be..288701ccbf7a 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -187,6 +187,9 @@ struct port { struct cdev *cdev; struct device *dev; + /* Reference-counting to handle port hot-unplugs and file operations */ + struct kref kref; + /* A waitqueue for poll() or blocking read operations */ wait_queue_head_t waitqueue; @@ -725,6 +728,8 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait) return ret; } +static void remove_port(struct kref *kref); + static int port_fops_release(struct inode *inode, struct file *filp) { struct port *port; @@ -745,6 +750,16 @@ static int port_fops_release(struct inode *inode, struct file *filp) reclaim_consumed_buffers(port); spin_unlock_irq(&port->outvq_lock); + /* + * Locks aren't necessary here as a port can't be opened after + * unplug, and if a port isn't unplugged, a kref would already + * exist for the port. Plus, taking ports_lock here would + * create a dependency on other locks taken by functions + * inside remove_port if we're the last holder of the port, + * creating many problems. + */ + kref_put(&port->kref, remove_port); + return 0; } @@ -757,6 +772,11 @@ static int port_fops_open(struct inode *inode, struct file *filp) port = find_port_by_devt(cdev->dev); filp->private_data = port; + /* Prevent against a port getting hot-unplugged at the same time */ + spin_lock_irq(&port->portdev->ports_lock); + kref_get(&port->kref); + spin_unlock_irq(&port->portdev->ports_lock); + /* * Don't allow opening of console port devices -- that's done * via /dev/hvc @@ -791,6 +811,7 @@ static int port_fops_open(struct inode *inode, struct file *filp) return 0; out: + kref_put(&port->kref, remove_port); return ret; } @@ -1079,6 +1100,7 @@ static int add_port(struct ports_device *portdev, u32 id) err = -ENOMEM; goto fail; } + kref_init(&port->kref); port->portdev = portdev; port->id = id; @@ -1183,22 +1205,43 @@ fail: return err; } -/* Remove all port-specific data. */ -static void remove_port(struct port *port) +/* No users remain, remove all port-specific data. */ +static void remove_port(struct kref *kref) +{ + struct port *port; + + port = container_of(kref, struct port, kref); + + sysfs_remove_group(&port->dev->kobj, &port_attribute_group); + device_destroy(pdrvdata.class, port->dev->devt); + cdev_del(port->cdev); + + kfree(port->name); + + debugfs_remove(port->debugfs_file); + + kfree(port); +} + +/* + * Port got unplugged. Remove port from portdev's list and drop the + * kref reference. If no userspace has this port opened, it will + * result in immediate removal the port. + */ +static void unplug_port(struct port *port) { struct port_buffer *buf; + spin_lock_irq(&port->portdev->ports_lock); + list_del(&port->list); + spin_unlock_irq(&port->portdev->ports_lock); + if (port->guest_connected) { port->guest_connected = false; port->host_connected = false; wake_up_interruptible(&port->waitqueue); - send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0); } - spin_lock_irq(&port->portdev->ports_lock); - list_del(&port->list); - spin_unlock_irq(&port->portdev->ports_lock); - if (is_console_port(port)) { spin_lock_irq(&pdrvdata_lock); list_del(&port->cons.list); @@ -1216,9 +1259,6 @@ static void remove_port(struct port *port) hvc_remove(port->cons.hvc); #endif } - sysfs_remove_group(&port->dev->kobj, &port_attribute_group); - device_destroy(pdrvdata.class, port->dev->devt); - cdev_del(port->cdev); /* Remove unused data this port might have received. */ discard_port_data(port); @@ -1229,11 +1269,19 @@ static void remove_port(struct port *port) while ((buf = virtqueue_detach_unused_buf(port->in_vq))) free_buf(buf); - kfree(port->name); - - debugfs_remove(port->debugfs_file); + /* + * We should just assume the device itself has gone off -- + * else a close on an open port later will try to send out a + * control message. + */ + port->portdev = NULL; - kfree(port); + /* + * Locks around here are not necessary - a port can't be + * opened after we removed the port struct from ports_list + * above. + */ + kref_put(&port->kref, remove_port); } /* Any private messages that the Host and Guest want to share */ @@ -1272,7 +1320,7 @@ static void handle_control_message(struct ports_device *portdev, add_port(portdev, cpkt->id); break; case VIRTIO_CONSOLE_PORT_REMOVE: - remove_port(port); + unplug_port(port); break; case VIRTIO_CONSOLE_CONSOLE_PORT: if (!cpkt->value) @@ -1686,7 +1734,7 @@ static void virtcons_remove(struct virtio_device *vdev) cancel_work_sync(&portdev->control_work); list_for_each_entry_safe(port, port2, &portdev->ports, list) - remove_port(port); + unplug_port(port); unregister_chrdev(portdev->chr_major, "virtio-portsdev"); |