To: linux-kernel@vger.kernel.org
From: Stephen Hemminger <shemminger@osdl.org>
Subject: Re: Hanged/Hunged process in Linux
Date: Wed, 4 May 2005 09:09:53 -0700
Organization: Open Source Development Lab
Message-ID: <20050504090953.20b57374@dxpl.pdx.osdl.net>
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On Wed, 04 May 2005 14:38:48 +0900
"Deepak" <deepakgaur@fastmail.fm> wrote:

> I am working on a Linux based system and developing a monitoring process
> which shall do the following function
> 
> (1) It will detect abnormally terminated application process and will
> restart the process group
> 
> (2) It will detect a hanged application and will restart it
> 
> My query is regarding second point . What should be the proper
> definition of a "Hanged Process" in Linux context . I searched on google
> regarding it and got the following definitions
> 
> (1) A process not accepting any signals and consuming system resources
> (2) A process in STOP state
> (3) A process in deadlock state
> 
> Process conforming to definition 3 will be due to race conditions/bad
> programming.Definition 1 does define a proper hanged process but is it
> possible to create such a process in LInux as in linux signal delivery
> to the process and its handling is assured by the Linux kernel.
> 
> Anybody having another definition for a "Hanged process" in Linux
> context
> 
> Deepak Gaur

It is impossible to absolutely tell the difference between a very busy process and one
that is hung.  Better to build to build hang detection into the process itself with
a heartbeat interface. Look at the hangcheck timer, nmi_watchdog, and watchdog
devices.
-- 
Stephen Hemminger	<shemminger@osdl.org>
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