Page Fault.

[Mel]

On Monday 01 December 2008 19:32:59 Keith wrote:
> Have a machine, Dell dual CPU/quad core Xeon. Runs FBSD 6.2.
> Custom kernel, with IPFW compiled in and using SMP.
>
> FreeBSD <hostname> 6.2-RELEASE FreeBSD 6.2-RELEASE #1: Wed Jan 23
> 12:17:29 PST 2008
>
> It runs, Dovecot, Postfix, Mysql, Apache. Standard email stuff. Put into
> production in March, ran perfect until July 29th when it rebooted by
> itself.
>
> It rebooted 2 more times in the last few months on its own. But in the
> last 6 weeks it has become a weekly occurance, with uptime no more than
> 6-7 days at most.
>
> The last 2 times I have cores and have run kgdb on them. Both vmcore's
> show the same things. Same pointers etc, the only difference is what the
> cpuid was at the time.
>
> ======
> kernel trap 12 with interrupts disabled
>
> Fatal trap 12: page fault while in kernel mode
> cpuid = 2; apic id = 02
> fault virtual address   = 0x104
> fault code              = supervisor read, page not present
> instruction pointer     = 0x20:0xc066ca51
> stack pointer           = 0x28:0xe6ec0c90
> frame pointer           = 0x28:0xe6ec0c9c
> code segment            = base 0x0, limit 0xfffff, type 0x1b
>                         = DPL 0, pres 1, def32 1, gran 1
> processor eflags        = resume, IOPL = 0
> current process         = 9 (thread taskq)
> trap number             = 12
> panic: page fault
> cpuid = 2
> Uptime: 6d6h23m45s
> Dumping 3327 MB (2 chunks)
>   chunk 0: 1MB (159 pages) ... ok
>   chunk 1: 3327MB (851624 pages) 3311 3295 3279 3263 3247 3231 3215 3199
> 3183 3167 3151 3135 3119 3103 3087 3071 3055 3039 3023 3007 2991 2975 2959
> 2943 2927 2911 2895 2879 2863 2847 2831 2815 2799 2783 2767 2751 2735 2719
> 2703 2687 2671 2655 2639 2623 2607 2591 2575 2559 2543 2527 2511 2495 2479
> 2463 2447 2431 2415 2399 2383 2367 2351 2335 2319 2303 2287 2271 2255 2239
> 2223 2207 2191 2175 2159 2143 2127 2111 2095 2079 2063 2047 2031 2015 1999
> 1983 1967 1951 1935 1919 1903 1887 1871 1855 1839 1823 1807 1791 1775 1759
> 1743 1727 1711 1695 1679 1663 1647 1631 1615 1599 1583 1567 1551 1535 1519
> 1503 1487 1471 1455 1439 1423 1407 1391 1375 1359 1343 1327 1311 1295 1279
> 1263 1247 1231 1215 1199 1183 1167 1151 1135 1119 1103 1087 1071 1055 1039
> 1023 1007 991 975 959 943 927 911 895 879 863 847 831 815 799 783 767 751
> 735 719 703 687 671 655 639 623 607 591 575 559 543 527 511 495 479 463
> 447 431 415 399 383 367 351 335 319 303 287 271 255 239 223 207 191 175
> 159 143 127 111 95 79 63 47 31 15
>
> #0  doadump () at pcpu.h:165
> 165             __asm __volatile("movl %%fs:0,%0" : "=r" (td));
> ============
>
> What might be the cause for this? It is the in the same place every time.
> Once the machine hung and had to be powercycled. But on the screen was the
> same page fault error on the same process.
>

frame 0 useless. You need the frame after calltrap().
And:

> instruction pointer     = 0x20:0xc066ca51
list *0xc066ca51

Generally a bt will show the needed information.
Likely cause: file system corruption, caused by background_fsck, but a 
backtrace should show more.


-- 
Mel

Problem with today's modular software: they start with the modules
    and never get to the software part.