Hi Stephen,
On Wed, Jul 22, 2015 at 03:52:53PM -0400, Stephen Chandler Paul wrote:
> +static int userio_char_open(struct inode *inode, struct file *file)
> +{
> + struct userio_device *userio;
> +
> + userio = devm_kzalloc(userio_misc.this_device,
> + sizeof(struct userio_device), GFP_KERNEL);
> + if (!userio)
> + return -ENOMEM;
Never ever use devm_ API outside of device probe() calls because
devm-managed resources only freed after failed probe() or after remove()
callback on driver model device and not any other device (block, char,
etc) in the system.
> +
> + spin_lock_init(&userio->head_lock);
> + mutex_init(&userio->tail_lock);
> + init_waitqueue_head(&userio->waitq);
> +
> + userio->serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
> + if (!userio->serio) {
> + devm_kfree(userio_misc.this_device, userio);
And indeed here you have ot manually release the acquired resource. So
the only benefit you got form devm* is wasted resousrces.
> + return -ENOMEM;
> + }
> +
> + userio->serio->write = userio_device_write;
> + userio->serio->port_data = userio;
> +
> + file->private_data = userio;
> +
> + return 0;
> +}
> +
> +static int userio_char_release(struct inode *inode, struct file *file)
> +{
> + struct userio_device *userio = file->private_data;
> +
> + if (userio->serio) {
> + userio->serio->port_data = NULL;
No need to reset, it is going away.
> +
> + if (userio->running)
> + serio_unregister_port(userio->serio);
> + else
> + kfree(userio->serio);
> + }
> +
> + devm_kfree(userio_misc.this_device, userio);
> +
> + return 0;
> +}
> +
> +static ssize_t userio_char_read(struct file *file, char __user *buffer,
> + size_t count, loff_t *ppos)
> +{
> + struct userio_device *userio = file->private_data;
> + int ret;
> + size_t nonwrap_len, copylen;
> +
> + if (!count)
> + return 0;
> +
> + if (file->f_flags & O_NONBLOCK && userio->head == userio->tail)
> + return -EAGAIN;
> + else {
This is racy. If there was data and other thread "stole" it here then
your O_NONBLOCK will block. See evdev_read() how you supposed to handle
this.
Thanks.
--
Dmitry
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