kern/164705: inability to terminate process in D state

[Andriy Gapon]

The following reply was made to PR kern/164705; it has been noted by GNATS.

From: Andriy Gapon <avg at icyb.net.ua>
To: bug-followup at FreeBSD.org, eugene at zhegan.in
Cc:  
Subject: Re: kern/164705: inability to terminate process in D state
Date: Thu, 02 Feb 2012 11:16:56 +0200

 Because you used words "completely ridiculous" in your bug report, I have to ask
 you what solution a genius like you can propose for a process which is stuck
 inside a system call (that is, in kernel).
 
 Now to techical side.  FreeBSD has no problem killing processes which execute in
 userland.  When a process is executing in kernel (in a system call), it is
 impossible to kill the process in a completely safe/clean fashion without
 affecting/corrupting internal kernel state.
 
 So bad news is that there will not be a universal kill command that can kill
 anything.
 
 Good news is that processes should never get stuck forever inside the kernel.
 Every time this happens it means that there is a (potentially new) bug in
 kernel, which should be properly reported and then hopefully fixed.
 
 So you will have to report concrete bugs with concrete diagnostics.
 
 See PR 164526 for a reference.
 
 P.S.  In my explanation I've omitted techicalities of kill sending a signal and
 how the signal is delivered to its target process.
 
 -- 
 Andriy Gapon