On Tue, May 19, 2015 at 04:06:53PM +0100, Richard Watts wrote:
> Avoid usb reset crashes by making tty_io cdevs truly dynamic
What USB reset crashes are you referring to here?
>
> Signed-off-by: Richard Watts <r...@kynesim.co.uk>
> Reported-by: Duncan Mackintosh <dmackint...@cbnl.com>
> ---
> drivers/tty/tty_io.c | 24 ++++++++++++++++--------
> include/linux/tty_driver.h | 2 +-
> 2 files changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index e569546..699cf20 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -3168,9 +3168,12 @@ static int tty_cdev_add(struct tty_driver *driver,
> dev_t dev,
> unsigned int index, unsigned int count)
> {
> /* init here, since reused cdevs cause crashes */
> - cdev_init(&driver->cdevs[index], &tty_fops);
> - driver->cdevs[index].owner = driver->owner;
> - return cdev_add(&driver->cdevs[index], dev, count);
> + driver->cdevs[index] = cdev_alloc();
> + if (!driver->cdevs[index])
> + return -ENOMEM;
> + cdev_init(driver->cdevs[index], &tty_fops);
> + driver->cdevs[index]->owner = driver->owner;
> + return cdev_add(driver->cdevs[index], dev, count);
> }
>
> /**
> @@ -3276,8 +3279,10 @@ struct device *tty_register_device_attr(struct
> tty_driver *driver,
>
> error:
> put_device(dev);
> - if (cdev)
> - cdev_del(&driver->cdevs[index]);
> + if (cdev) {
> + cdev_del(driver->cdevs[index]);
> + driver->cdevs[index] = NULL;
> + }
> return ERR_PTR(retval);
> }
> EXPORT_SYMBOL_GPL(tty_register_device_attr);
> @@ -3297,8 +3302,10 @@ void tty_unregister_device(struct tty_driver *driver,
> unsigned index)
> {
> device_destroy(tty_class,
> MKDEV(driver->major, driver->minor_start) + index);
> - if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC))
> - cdev_del(&driver->cdevs[index]);
> + if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
> + cdev_del(driver->cdevs[index]);
> + driver->cdevs[index] = NULL;
> + }
> }
> EXPORT_SYMBOL(tty_unregister_device);
>
> @@ -3363,6 +3370,7 @@ err_free_all:
> kfree(driver->ports);
> kfree(driver->ttys);
> kfree(driver->termios);
> + kfree(driver->cdevs);
> kfree(driver);
> return ERR_PTR(err);
> }
> @@ -3391,7 +3399,7 @@ static void destruct_tty_driver(struct kref *kref)
> }
> proc_tty_unregister_driver(driver);
> if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)
> - cdev_del(&driver->cdevs[0]);
> + cdev_del(driver->cdevs[0]);
> }
> kfree(driver->cdevs);
> kfree(driver->ports);
> diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
> index 92e337c..1610524 100644
> --- a/include/linux/tty_driver.h
> +++ b/include/linux/tty_driver.h
> @@ -296,7 +296,7 @@ struct tty_operations {
> struct tty_driver {
> int magic; /* magic number for this structure */
> struct kref kref; /* Reference management */
> - struct cdev *cdevs;
> + struct cdev **cdevs;
> struct module *owner;
> const char *driver_name;
> const char *name;
I don't understand what bug this patch is trying to solve, care to help
describe it better?
thanks,
greg k-h
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