Double panics with g_up

[Andrey Chernov]

I saw this already 5 times. It is _always_ double panic. Second panic may 
vary (f.e. clock, etc) but first one _always_ in g_up. Since second panic 
is on the way, there is no usable stack trace remains.

My suggestion: can we add sysctl to NOT sync disk after panic but reboot 
immediately to preserve stack frame (for remote machine)?

Fatal trap 12: page fault while in kernel mode
fault virtual address = 0x24
fault code            = supervisor read, page not present
instruction pointer   = 0x8:0xc017fd3b
stack pointer         = 0x10:0xcd36bb70
frame pointer         = 0x10:0xcd36bb84
code segment          = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags      = interrupt enabled, resume, IOPL = 0
current process               = 3 (g_up)
trap number           = 12
panic: page fault

syncing disks, buffers remaining...

Fatal trap 12: page fault while in kernel mode
fault virtual address = 0x24
fault code            = supervisor read, page not present
instruction pointer   = 0x8:0xc017fd3b
stack pointer         = 0x10:0xcd377c84
frame pointer         = 0x10:0xcd377c98
code segment          = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags      = interrupt enabled, resume, IOPL = 0
current process               = 24 (irq15: ahc0)
trap number           = 12
panic: page fault
Uptime: 2d3h22m53s