r212281 breaks KDE

Sun Sep 12 14:43:02 UTC 2010

For the last week, on and off, I've been looking for something that
caused KDE to be horridly unstable, i.e. machine freezes with and
without a core-dump.

Removing r212281 (and r212282) restores that stability. Is there a race
condition that this update exposes by reducing lock strength?

The most common failure with this code included produces a back-trace
similar to the one attached,

	imb
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toshi.auburn.protected-networks.net dumped core - see /var/crash/vmcore.0

Sat Sep 11 15:33:22 EDT 2010

FreeBSD toshi.auburn.protected-networks.net 9.0-CURRENT FreeBSD 9.0-CURRENT #5 r212466M: Sat Sep 11 10:10:59 EDT 2010     root at toshi.auburn.protected-networks.net:/usr/obj/usr/home/imb/svn/head/sys/TOSHI  i386

panic: page fault

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Unread portion of the kernel message buffer:

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address	= 0x22c
fault code		= supervisor read, page not present
instruction pointer	= 0x20:0xc066705a
stack pointer	        = 0x28:0xe944b7f8
frame pointer	        = 0x28:0xe944b810
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		= 1938 (kdeinit4)
trap number		= 12
panic: page fault
cpuid = 0
Uptime: 2m33s
Physical memory: 3049 MB
Dumping 225 MB: 210 194 178 162 146 130 114 98 82 66 50 34 18 2

Reading symbols from /boot/modules/vboxdrv.ko...done.
Loaded symbols for /boot/modules/vboxdrv.ko
Reading symbols from /boot/modules/vboxnetflt.ko...done.
Loaded symbols for /boot/modules/vboxnetflt.ko
Reading symbols from /boot/modules/vboxnetadp.ko...done.
Loaded symbols for /boot/modules/vboxnetadp.ko
Reading symbols from /usr/local/modules/fuse.ko...done.
Loaded symbols for /usr/local/modules/fuse.ko
#0  doadump () at pcpu.h:231
231	pcpu.h: No such file or directory.
	in pcpu.h
(kgdb) #0  doadump () at pcpu.h:231
#1  0xc06760f7 in boot (howto=260)
    at /usr/home/imb/svn/head/sys/kern/kern_shutdown.c:416
#2  0xc06764e8 in panic (fmt=0x104 <Address 0x104 out of bounds>)
    at /usr/home/imb/svn/head/sys/kern/kern_shutdown.c:590
#3  0xc09950ff in trap_fatal (frame=0xe944b7b8, eva=40)
    at /usr/home/imb/svn/head/sys/i386/i386/trap.c:980
#4  0xc0995469 in trap_pfault (frame=0xe944b7b8, usermode=0, eva=556)
    at /usr/home/imb/svn/head/sys/i386/i386/trap.c:893
#5  0xc09958f7 in trap (frame=0xe944b7b8)
    at /usr/home/imb/svn/head/sys/i386/i386/trap.c:568
#6  0xc097e16c in calltrap ()
    at /usr/home/imb/svn/head/sys/i386/i386/exception.s:168
#7  0xc066705a in _mtx_lock_sleep (m=0xc81c26e8, tid=3343885696, opts=0, 
    file=0x0, line=0) at /usr/home/imb/svn/head/sys/kern/kern_mutex.c:369
#8  0xc09385d8 in vnode_create_vobject (vp=0xc825a330, isize=512, 
    td=0xc74fa580) at /usr/home/imb/svn/head/sys/vm/vnode_pager.c:111
#9  0xc0904751 in ufs_lookup_ino (vdp=0xc825a330, vpp=0xe944bb40, 
    cnp=0xe944bb54, dd_ino=0x0)
    at /usr/home/imb/svn/head/sys/ufs/ufs/ufs_lookup.c:260
#10 0xc0905370 in ufs_lookup (ap=0xe944b97c)
    at /usr/home/imb/svn/head/sys/ufs/ufs/ufs_lookup.c:215
#11 0xc06f9cc6 in vfs_cache_lookup (ap=0xe944ba08) at vnode_if.h:80
#12 0xc09b2811 in VOP_LOOKUP_APV (vop=0xc0ac7480, a=0xe944ba08)
    at vnode_if.c:123
#13 0xc0700e89 in lookup (ndp=0xe944bb28) at vnode_if.h:54
#14 0xc070218c in namei (ndp=0xe944bb28)
    at /usr/home/imb/svn/head/sys/kern/vfs_lookup.c:268
#15 0xc0711513 in kern_statat_vnhook (td=0xc74fa580, flag=0, fd=-100, 
    path=0x2b2aa050 <Address 0x2b2aa050 out of bounds>, 
    pathseg=UIO_USERSPACE, sbp=0xe944bbe4, hook=0)
    at /usr/home/imb/svn/head/sys/kern/vfs_syscalls.c:2352
#16 0xc07116b7 in kern_statat (td=0xc74fa580, flag=0, fd=-100, 
    path=0x2b2aa050 <Address 0x2b2aa050 out of bounds>, 
    pathseg=UIO_USERSPACE, sbp=0xe944bbe4)
    at /usr/home/imb/svn/head/sys/kern/vfs_syscalls.c:2333
#17 0xc07117db in kern_stat (td=0xc74fa580, 
    path=0x2b2aa050 <Address 0x2b2aa050 out of bounds>, 
    pathseg=UIO_USERSPACE, sbp=0xe944bbe4)
    at /usr/home/imb/svn/head/sys/kern/vfs_syscalls.c:2325
#18 0xc071186f in stat (td=0xc74fa580, uap=0xe944bcec)
    at /usr/home/imb/svn/head/sys/kern/vfs_syscalls.c:2294
#19 0xc06b4087 in syscallenter (td=0xc74fa580, sa=0xe944bce4)
    at /usr/home/imb/svn/head/sys/kern/subr_trap.c:319
#20 0xc09954cc in syscall (frame=0xe944bd28)
    at /usr/home/imb/svn/head/sys/i386/i386/trap.c:1095
#21 0xc097e1d1 in Xint0x80_syscall ()
    at /usr/home/imb/svn/head/sys/i386/i386/exception.s:266
#22 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb) 