doing a callback from the kernel to userspace

[Sebastian Heidl <heidl@zib.de>]

Hi,

I read some of the signaling code and must admit that I could not extract the
necessary information from it. Ideally I'd like to call a user-supplied function
having just a pointer to this function and say the task_struct of the owning
process.
What steps are needed to savely do the callback ?  (How) can I retrieve the
necessary information from the task_struct ?

any pointers are welcome
_sh_

PS: Yes, I really do need this as signals form the kernel to userspace add to
    much latency (10 to 20 usecs) and I want to avoid waiting in a system call.