User space <==> kernel space for device wakeups.

[Greg Kroah-Hartman]

On Wed, Oct 08, 2014 at 05:57:50PM +0200, Kristof Provost wrote:
> On 2014-10-08 21:14:43 (+0530), Jeshwanth Kumar N K <jeshkumar555 at gmail.com> wrote:
> > Wayback when I was working on some project to wake up userspace program for
> > every rising edge in GPIO pin (hall sensor), I use to send signal to the
> > PID from kernel, before that userspace has to register its PID with kernel
> > module. 
> > 
> I've seen a certain vendor[1] do something similar. They saved the task
> pointer for whichever process made the magical ioctl() call and used it
> to send signals from the interrupt handler. It worked, right up to the
> point where the process went away and then the kernel panicked.

Exactly, don't do that :)

Finding out the real problem that is attempting to be solved would be
good...

greg k-h