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Re: subshell (ctrl-o) not working properly

Subject: Re: subshell (ctrl-o) not working properly
From: Tomasz Chmielewski
Date: Mon, 27 Feb 2006 16:27:46 +0100
Pavel Tsekov wrote:


Pressing ctrl + o shows the background, but I can't execute any shell
commands (I return to mc immediately when pressing any key).

Strace available at http://wpkg.org/subshell.strace.gz (strace -o
subshell.strace) and http://wpkg.org/sub.strace.gz (strace -o sub.strace
mc -U).
The strace output suggests that the subshell is being killed by a SIGPWR
signal. I cannot tell why this signal is being sent to the subshell
though. Maybe the OS you are running on your embedded device is
sending this signal for some specific purpose and expects the application
to deal with it... In any case the fact that the subshell is not working
on your platform is not a bug in MC.
Perhaps the subshell consumes so much resources on this tiny router that
 the kernel reports a power failure (that's what SIGPWR is) and kills
the subshell :)
It's a regular Linux 2.4.30, a major difference is that it's not using
glibc, but uClibc, and not a x86 processor, but a mipsel one.
In linux-2.4.30/include/asm-i386/signal.h it's:

#define SIGPWR          30

and in linux-2.4.30/include/asm-mips/signal.h it's:

#define SIGPWR          19      /* Power failure restart (System V).  */

and once again in linux-2.4.30/include/asm-mips/offset.h:

#define _SIGPWR     0x13:

Not being a kernel hacker, this tells me that the only way to get subshell working for me would be to make it ignore the SIGPWR I guess?

Tomasz Chmielewski
WPKG - http://wpkg.org
Software deployment with Samba
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