signal design questions

[Wenyen, Shih]

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

___________________________________________________ 
 您的生活即時通 － 溝通、娛樂、生活、工作一次搞定！ 
 http://messenger.yahoo.com.tw/