On Thu, 28 Jul 2005, Frank McConnell wrote:

--- begin paste ---
Fatal trap 12: page fault while in kernel mode
fault virtual address  = 0x24
fault code             = supervisor read, page not present
instruction pointer    = 0x8:0xc03db1cf
stack pointer          = 0x10:0xeb328c64
frame pointer          = 0x10:0xeb328c78
code segment           = base 0x0, limit 0xfffff, type 0x1b
                      = DPL 0, pres 1, def32 1, gran 1
processor eflags       = resume, IOPL = 0
current process        = 70 (pagedaemon)
[thread pid 70 tid 100080 ]
Stopped at      0xc03db1cf = propagate_priority+0x7f:  movl    0x24(%eax),%eax
db> trace
Tracing pid 70 tid 100080 td 0xc6a89000
propagate_priority(c6a89000,c0628280,c0636c60,c6a89000,c6cdaa82) at 0xc03db1cf 
= propagate_priority+0x7f
turnstile_wait(c6a6f240,c0636c60,c6cdaa80) at 0xc03db84a = turnstile_wait + 
0x266
_mtx_lock_sleep(c0636c60,c6a89000,0,0,0) at 0xc03b4c25 = _mtx_lock_speed+0xad
msleep(c0637104,c0636c60,44,c059aa74,1f4) at 0xc03c37ea = msleep+0x39a
vm_pageout(0,eb328d38) at 0xc04fb0e4 = vm_pageout+0x280
fork_exit(c04fae64,0,eb328d38) at 0xc03a8680 = fork_exit+0x74
fork_trampoline() at 0xc0539d9c = fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xeb328d6c, ebp = 0 ---
db>

This appears to be a NULL pointer dereference in propagate_priotity(). Often a panic in propagate_priority is actually a symptom of a slightly earlier problem which is discovered by propagate_priority when it trips over, for example, a bad mutex. If you're set up with a serial port to copy and paste debugging output, the output of 'ps' and 'show pcpu' for each of the cpus (as well as 'show pcpu without a cpu argument) would be helpful. It wouldn't hurt also to use gdb on a copy of the kernel with debugging sybols to map 'vm_pageout+0x280' into a line number. Details on these various activities can be found in the handbook.

Robert N M Watson
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