Re: Can a user app hang a *IX system?

From: Måns Rullgård (mru_at_inprovide.com)
Date: 01/27/05 

Date: Thu, 27 Jan 2005 01:58:46 +0100

"JimW" <j1mw_nospam_plz@bellsouth.net> writes:

> I have a situation where our program(s) completely hang the system.
> OS is MontaVista Embedded Linux on a xscale big-endian cpu.
> Our app starts and hangs, and also hangs the system, can't ctrl-brk the app;
> can't use console, can't telnet (not a rejected connection, just hangs
> during the connect). I can, however, ping the system (thanks for small
> favors).
>
> I tried using gdb to attach to the process, and gdb also hangs.
> Further, while building the app, if I had a large no. of objects, it would
> also hang during the link for the shared library - by breaking it up into
> multiple .so files, it succeeded.
>
> It's obviously a resource problem, but I thought most *IX systems would
> start grumbling about running out before just dying.
>
> I have a smaller app that tests the no. of threads, semaphores, and files
> and it behaves normally - running out with about 500 thrds and 127
> semaphores.
>
> This is a very large app and is obviously way too big for the system (64mb),
> but should it be able to hang totally. The apps is fairly stable and runs
> fine on AIX, Linux RH, HP, Solaris.
>
> Any insight before I start flooding it with printfs???

Are you by chance running out of memory so the system starts swapping
heavily? This can make the system appear to be hung, even if it is
making slow progress. 

-- 
Måns Rullgård
mru@inprovide.com

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