signal design questions

[Garrett Cooper]

On Nov 11, 2006, at 10:55 AM, Wenyen, Shih wrote:

> Hi all,
>    I have some questions.
>    (1)  I know how to delivery of a signal to a
> process.
>
>       1. The kernel places a signal context on the
> user's stack.(user level)
>       2. The kernel places a signal-handler frame on
> the user's stack.(kernel level)
>       3. The user's signal handler returns to the
> sigtramp() routine, which pops the signal-handler
> context from the user's stack.(user level)
>       4. The sigtramp() routine finishes by calling
> the sigreturn system call.
>
>       But, why don't implement signal handler routine
> in kernel level? Are there having any ideas to
> implement signal handler routine in kernel level?
>
>
>     (2) The system-call exit code first checks for a
> posted signal and check to see whether any process has
> a priority higher than that of the currently running
> process.
>     But, I don't know the signal be checked when
> returning from kernel mode to user mode.
>
>     Anyone have any other methods to checked the
> signal in the other occasion ?
>
> Thanks,
>
> Wenyen

I would suggest asking this question on the freebsd-hackers list.
-Garrett