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Re: kern/39307 (mfs will sometimes panic at umount time)

Subject: Re: kern/39307 mfs will sometimes panic at umount time
From: Izumi Tsutsui
Date: Thu, 25 Sep 2008 00:32:43 +0900
> Synopsis: mfs will sometimes panic at umount time
 :
> Should be fixed - please verify.

A cobalt kernel (in restorecd, which uses mfs for many dirs)
still fails:
---
NetBSD 4.99.72 (GENERIC) #1: Wed Sep 24 23:50:46 JST 2008
        
tsutsui@mirage:/home/tsutsui/cobalt/restorecd/usr/src/sys/arch/cobalt/compile/obj.cobalt/GENERIC
Cobalt Qube 2
total memory = 65536 KB
avail memory = 59624 KB
mainbus0 (root)
com0 at mainbus0 addr 0x1c800000 level 3: st16650a, working fifo
com0: console
cpu0 at mainbus0: QED RM5200 CPU (0x28a0) Rev. 10.0 with built-in FPU Rev. 10.0
cpu0: 32KB/32B 2-way set-associative L1 Instruction cache, 48 TLB entries
cpu0: 32KB/32B 2-way set-associative write-back L1 Data cache

 :

Sep 24 23:39:27 client reboot: rebooted by root
Sep 24 23:39:27 client syslogd: Exiting on signal 15
trap: TLB miss (load or instr. fetch) in kernel mode
status=0xff03, cause=0x8, epc=0x802f99f8, vaddr=0xc6474034
pid=125 cmd=mount_mfs usp=0x7fffca00 ksp=0xc6481d10
Stopped in pid 125.1 (mount_mfs) at     netbsd:atomic_dec_uint_nv+0x18: lw      
s0,0(s2)
db> tr
atomic_dec_uint_nv+18 (c6474034,83c21ab4,0,0) ra 80256184 sz 32
vfs_destroy+18 (c6474034,83c21ab4,0,0) ra 8025d3ec sz 24
do_sys_mount+814 (83c57800,83c21ab4,0,7fffef94) ra 8025d430 sz 256
sys___mount50+3c (83c57800,83c21ab4,c6481f68,7fffef94) ra 802a24a0 sz 48
syscall_plain+130 (83c57800,83c21ab4,c6481f68,7fffef94) ra 8029bffc sz 80
mips3_SystemCall+bc (83c57800,83c21ab4,c6481f68,7fffef94) ra 7de3d7b0 sz 0
PC 0x7de3d7b0: not in kernel space
0+7de3d7b0 (83c57800,83c21ab4,c6481f68,7fffef94) ra 0 sz 0
User-level: pid 125.1
db> 
---
Note 'umount -a' before reboot(8) (though it fails to umount mfs
due to device busy) seems to prevent the panic.


i386 GENERIC kernel (which is a cdroot server of cobalt restorecd,
also uses mfs heavily) also fails:
---
NetBSD 4.99.72 (GENERIC) #0: Wed Sep 24 23:59:51 JST 2008
        
tsutsui@mirage:/home/tsutsui/cobalt/restorecd/usr/src/sys/arch/i386/compile/obj.i386/GENERIC
total memory = 767 MB
avail memory = 742 MB
VIA Technologies, Inc. VT8363 ( )
mainbus0 (root)
cpu0 at mainbus0: AMD 686-class, 1300MHz, id 0x671
acpi0 at mainbus0: Intel ACPICA 20080321

 :

bootserver# reboot
Sep 24 15:18:15 uvm_fault(0xcadb98f0, 0, 1) -> 0xe
fatal page faultbootserver reboo in supervisor mode
trap type 6 code 0 eip c047c6e9 cs 8 eflags 10206 cr2 8 ilevel 0
kernel: supervisor trap page fault, code=0
Stopped in pid 60.1 (mount_mfs) at      netbsd:bt_rembusy+0x9:  movl    
0x8(%edx),%ecx
db{0}> tr
bt_rembusy(c1ad2800,c1ad2800,cc29dca0,cc1c8000,0,1,cc1ebb8c,c0472fe1,c1ad2800,cc1c8000)
 at netbsd:bt_rembusy+0x9
vmem_xfree(c1ad2800,cc1c8000,910,c04ac8b6,c0b0c260,cc1c8000,cc1ebbac,c04b21ca,cc1c8000,910)
 at netbsd:vmem_xfree+0x46
kmem_free(cc1c8000,910,cc286b90,1286a20,cc286a20,cc286a20,cc1ebcbc,c04b8fec,cc1c8000,0)
 at netbsd:kmem_free+0x21
vfs_destroy(cc1c8000,0,0,cc1ebce0,0,0,cc1ebbfc,cc1ebbf8,1da6f00,c1b9f300) at 
netbsd:vfs_destroy+0x7a
do_sys_mount(cc29dca0,0,8050db7,bfbfff96,5c,bfbfecc0,0,78,cc1ebd28,cc29dca0) at 
netbsd:do_sys_mount+0x9ac
sys___mount50(cc29dca0,cc1ebd00,cc1ebd28,8050db7,bfbfff96,5c,bfbfecc0,78,64,8051040)
 at netbsd:sys___mount50+0x49
syscall(cc1ebd48,b3,ab,bfbf001f,bbbc001f,0,bfbfeec4,bfbfee48,0,bfbfecc0) at 
netbsd:syscall+0xa0
db{0}> 
---
Izumi Tsutsui

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