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@(#)crash.8 4.1 (Berkeley) 04/27/85
When the system crashes voluntarily it prints a message of the form
panic: why i gave up the ghoston the console, takes a dump on a mass storage peripheral, and then invokes an automatic reboot procedure as described in reboot (8). (If auto-reboot is disabled on the front panel of the machine the system will simply halt at this point.) Unless some unexpected inconsistency is encountered in the state of the file systems due to hardware or software failure the system will then resume multi-user operations.
The system has a large number of internal consistency checks; if one of these fails, then it will panic with a very short message indicating which one failed.
The most common cause of system failures is hardware failure, which can reflect itself in different ways. Here are the messages which you are likely to encounter, with some hints as to causes. Left unstated in all cases is the possibility that hardware or software error produced the message in some unexpected way.
IO err in push .ns
hard IO err in swap The system encountered an error trying to write to the paging device or an error in reading critical information from a disk drive. You should fix your disk if it is broken or unreliable.
timeout table overflow .ns This really shouldn't be a panic, but until we fix up the data structure involved, running out of entries causes a crash. If this happens, you should make the timeout table bigger.
KSP not valid .ns
SBI fault .ns
CHM? in kernel These indicate either a serious bug in the system or, more often, a glitch or failing hardware. If SBI faults recur, check out the hardware or call field service. If the other faults recur, there is likely a bug somewhere in the system, although these can be caused by a flakey processor. Run processor microdiagnostics.
machine check %x: description .ns
\0\0\0machine dependent machine-check information .ns We should describe machine checks, and will someday. For now, ask someone who knows (like your friendly field service people).
trap type %d, code=%d, pc=%x A unexpected trap has occurred within the system; the trap types are:
0 reserved addressing fault 1 privileged instruction fault 2 reserved operand fault 3 bpt instruction fault 4 xfc instruction fault 5 system call trap 6 arithmetic trap 7 ast delivery trap 8 segmentation fault 9 protection fault 10 trace trap 11 compatibility mode fault 12 page fault 13 page table fault
The favorite trap type in system crashes is trap type 9, indicating a wild reference. The code is the referenced address, and the pc at the time of the fault is printed. These problems tend to be easy to track down if they are kernel bugs since the processor stops cold, but random flakiness seems to cause this sometimes, e.g. we have trapped with code 80000800 three times in six months as an instruction fetch went across this page boundary in the kernel but have been unable to find any reason for this to have happened.
init died The system initialization process has exited. This is bad news, as no new users will then be able to log in. Rebooting is the only fix, so the system just does it right away.
That completes the list of panic types you are likely to see.
When the system crashes it write (or at least attempts to write) a image of the current memory into the back end of the primary swap area. After the system is rebooted, the program savecore (8) runs and preserves a copy of this core image and the current system in a specified directory for later perusal. See savecore (8) for details.
To analyze a dump you should begin by running "ps -alxk" to print the process table at the time of the crash. Use adb (1) to examine /vmcore . The location _rpb+0t508 is the bottom of a stack onto which were pushed the stack pointer sp , PCBB (containing the physical address of a u_area ), MAPEN , IPL , and registers r13 - r0 (in that order). r13 (fp) is the system frame pointer and the stack is used in standard calls format. Use adb (1) to get a reverse calling order. In most cases this procedure will give an idea of what is wrong. A more complete discussion of system debugging is impossible here. See, however, analyze (8) for some more hints.
"VAX 11/780 System Maintenance Guide" for more information about machine checks.