Bug 232075

Summary: 12-ALPHA8 page fault in kernel mode
Product: Base System Reporter: Jeremy Faulkner <gldisater>
Component: kernAssignee: freebsd-bugs (Nobody) <bugs>
Status: New ---    
Severity: Affects Only Me CC: linimon
Priority: --- Keywords: regression
Version: CURRENT   
Hardware: amd64   
OS: Any   

Description Jeremy Faulkner 2018-10-08 15:54:28 UTC
Fatal trap 12: page fault while in kernel mode
cpuid = 13; apic id = 33
fault virtual address = 0x3c8
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xfffffffff80b94b64
stack pointer = 0x28:0xfffffe017d0f85c0
frame pointer = 0x28:0cfffffe017d0f85f0
code segment = base rx0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 2625 (zfs)
[ thread pid 2625 tid 102072 ]
Stopped at _sx_xlock+0x44: movq 0x18(%rbx),%rax

system was under moderate load doing a zfs send/recv from one drive into the main pool while trying to unmount some zfs datasets. kernel dump to follow.
Comment 1 Mark Linimon freebsd_committer freebsd_triage 2018-10-09 15:41:11 UTC
Is this an upgrade from an earlier version?  (so that I can classify it 'regression')
Comment 2 Jeremy Faulkner 2018-10-09 20:59:02 UTC
This system was upgraded from 11.2-RELENG branch to 12-ALPHA by cloning the boot environment, and then building from source. I forget exactly which ALPHA 4, or 5 but it's currently at 8.

And the promised core file:

tar zcvf pagefault.tar.gz /boot/kernel /var/crash/*.5

Comment 3 Jeremy Faulkner 2018-10-09 23:27:54 UTC
tar.gz of  /usr/lib/debug/boot/kernel

Comment 4 Jeremy Faulkner 2018-10-11 01:44:28 UTC
Some more info, I was able to cause another page fault while in kernel mode, wasn't able to dump it. It started to dump but didn't get to 1% after 30 mins so I powercycled the system. This might be caused by two zfs datasets having the same mount point and trying to unmount one of them.