Re: [PATCH v2 (resend)] media: imon: reorganize serialization

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, May 02, 2022 at 10:04:22PM +0900, Tetsuo Handa wrote:
> On 2022/05/02 21:53, Greg KH wrote:
> >> @@ -153,6 +153,24 @@ struct imon_context {
> >>  	const struct imon_usb_dev_descr *dev_descr;
> >>  					/* device description with key */
> >>  					/* table for front panels */
> >> +	/*
> >> +	 * Fields for deferring free_imon_context().
> >> +	 *
> >> +	 * Since reference to "struct imon_context" is stored into
> >> +	 * "struct file_operations"->private_data, we need to remember
> >> +	 * how many file descriptors might access this "struct imon_context".
> >> +	 */
> >> +	refcount_t users;
> > 
> > Are you sure this is going to work properly?
> > 
> > How do you handle userspace passing around file descriptors to other
> > processes?
> > 
> > You really should not ever have to count this.
> 
> Passing around file descriptors results in nothing but delay of freeing memory.
> Is this so fatal problem?

Not at all, it's just that any driver that tries to count open calls
usually is wrong as they forget about this type of thing, which is why I
asked.

thanks,

greg k-h