From owner-freebsd-hackers@FreeBSD.ORG Fri Dec 16 09:13:57 2005 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0D18916A41F for ; Fri, 16 Dec 2005 09:13:57 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (lurza.secnetix.de [83.120.8.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id 48B7143D6A for ; Fri, 16 Dec 2005 09:13:56 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (qnunef@localhost [127.0.0.1]) by lurza.secnetix.de (8.13.4/8.13.4) with ESMTP id jBG9DsEm000451; Fri, 16 Dec 2005 10:13:55 +0100 (CET) (envelope-from oliver.fromme@secnetix.de) Received: (from olli@localhost) by lurza.secnetix.de (8.13.4/8.13.1/Submit) id jBG9Dshc000450; Fri, 16 Dec 2005 10:13:54 +0100 (CET) (envelope-from olli) Date: Fri, 16 Dec 2005 10:13:54 +0100 (CET) Message-Id: <200512160913.jBG9Dshc000450@lurza.secnetix.de> From: Oliver Fromme To: freebsd-hackers@freebsd.org, "roma.a.g" In-Reply-To: <200512160846.jBG8kaEB099405@lurza.secnetix.de> X-Newsgroups: list.freebsd-hackers User-Agent: tin/1.5.4-20000523 ("1959") (UNIX) (FreeBSD/4.11-STABLE (i386)) Cc: Subject: Re: easy question about kill command X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-hackers@freebsd.org, "roma.a.g" List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Dec 2005 09:13:57 -0000 Oliver Fromme wrote: > roma.a.g wrote: > > Is there anyone who can explain me, why when i say 'kill -HUP id', > > and its failed to restart, kill say nothing? > > Because the kill command has no way to know about it. > > The kill command only instructs the kernel to deliver > a signal to a process (or to a process group). The only > feedback it gets from the kernel is whether the target > process exists or not. (The latter is often used to > check for the existence of a particular process ID, by > trying to send it a "zero" signal which does nothing.) Oh, I forgot to add one further fact: The target process can only respond to the signal the next time it gets a time slice from the scheduler. That doesn't necessarily need to be immediately. For example, when the process is currently blocked (waiting for I/O or another resource), it can be a long time until it gets a chance to respond to the signal. At that time, the kill process has probably already exited. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "It combines all the worst aspects of C and Lisp: a billion different sublanguages in one monolithic executable. It combines the power of C with the readability of PostScript." -- Jamie Zawinski, when asked: "What's wrong with perl?"