Date: Sun, 2 Jul 1995 14:50:28 +1000 From: Bruce Evans <bde@zeta.org.au> To: hackers@freebsd.org, matt@lkg.dec.com Subject: Re: Best way to diagnose system lockups? Message-ID: <199507020450.OAA32661@godzilla.zeta.org.au>
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>When the system locks up, neither DDB (via CTRL/ALT/ESC) nor hardclock >(no watchdog panic fires) is called. The only way back is reset which >of course doesn't result in any useful information. (damn it! I like >machines with halt buttons (like a VAX or an Alpha). Sigh) I Ctrl-Alt-Esc doesn't work, then the system must be wedged at spltty or splclock (unfortunately splimp is higher than spltty if slip or ppp is configured, so wedging at splimp makes it difficult to enter ddb). I usually remove the keyboard bit (1<<1) from tty_imask to debug wedging at spltty. This is perfectly safe if you don't touch the keyboard and fairly safe (perhaps perfectly safe) even if you do (the keyboard intr handler sets the bit although spltty() doesn't). Bruce
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