Subject: Re: kern/31902: kern uvm_sched crash
To: None <gnats-bugs@netbsd.org>
From: Chuck Silvers <chuq@chuq.com>
List: netbsd-bugs
Date: 10/24/2005 06:10:22
hi,

On Mon, Oct 24, 2005 at 12:53:00AM +0000, lamer0@lamer0.com wrote:
> 	When swap gets low on space the kernel panics.
...
> cpu_Debugger(4,0,0,ab517e98,800) at netbsd:cpu_Debugger+0x4
> comintr(c0855c00,0,c0510010,c0260030,c0490010) at netbsd:comintr+0xcd
> Xintr_legacy4() at netbsd:Xintr_legacy4+0xa9
> --- interrupt ---
> cpu_switch(c0496640,0,1,0,0) at netbsd:cpu_switch+0x9f
> ltsleep(c0496480,4,c03f2330,0,0) at netbsd:ltsleep+0x207
> uvm_scheduler(c0496460,1,c051300c,513000,51b000) at netbsd:uvm_scheduler+0x76
> setrootfstime(0,0,0,0,0) at netbsd:setrootfstime

this stack trace does not indicate that the machine has paniced,
but rather that the serial console has received the input (a serial BREAK
by default) that tells it to enter the debugger.  perhaps the cable
is flakey and generating spurious BREAKs?  power-cycling whatever is at
the other end of the cable will often do this as well.

you can change the input sequence that enters the debugger by using (eg.)
	sysctl -w hw.cnmagic=+++

or you can disable entering the debugger from the console entirely with
	sysctl -w ddb.fromconsole=0

-Chuck