I got a panic on NetBSD 1.5ZA from Jan 4 on a AMD K6-2 with 128MB RAM. I
was in the middle of compiling Mozilla... kernel with debug symbols and
the crash dump file are available if they'll be helpful.

panic: pmap_change_attrs: mapping without PTP detected
Begin traceback...
pmap_change_attrs(c04995ec,0,40,283) at pmap_change_attrs+0xd5
genfs_putpages(cb033d40,0,cb033d58,c36aa640,0) at genfs_putpages+0x43f
VOP_PUTPAGES(cb1e93f8,0,0,0,0,11,0,0) at VOP_PUTPAGES+0x49
ffs_full_fsync(cb033e58,cb1e93f8,c0682000,c0163a56,0) at ffs_full_fsync+0x89
ffs_fsync(cb033e58,10012,c0642840,cb033e48,cb1e93f8) at ffs_fsync+0x3c
VOP_FSYNC(cb1e93f8,c05ebe80,0,0,0,0,0,cb034004) at VOP_FSYNC+0x58
ffs_sync(c0659600,3,c05ebe80,cb034004) at ffs_sync+0xcf
sync_fsync(cb033f28,0,cb033f2c,c0165e2f,ffffffff) at sync_fsync+0x5c
VOP_FSYNC(cb0e573c,c05ebe80,8,0,0,0,0,cb034004) at VOP_FSYNC+0x58
sched_sync(cb034004) at sched_sync+0xb1
End traceback...
syncing disks... panic: lockmgr: locking against myself
Begin traceback...
lockmgr(cb1e9464,10012,cb1e93f8,c023687a,cb033a68) at lockmgr+0x591
genfs_lock(cb033a30,0,cb033a3c,c0165e2f,cb2227d4) at genfs_lock+0x1c
VOP_LOCK(cb1e93f8,10012,cb033a9c,cb31fdac) at VOP_LOCK+0x2e
vn_lock(cb1e93f8,10012,0,0,cb1e93f8) at vn_lock+0x5d
vget(cb1e93f8,10012,0,cb034004) at vget+0xcd
ffs_sync(c0659600,2,c05ebe80,cb034004) at ffs_sync+0x9b
sys_sync(cb034004,0,0,c0143af8,100) at sys_sync+0x5a
vfs_shutdown(cb033ba8,1,fff6,c02c2852,c0143a6c) at vfs_shutdown+0x6a
cpu_reboot(100,0,6,0,c07246e0) at cpu_reboot+0x3b
panic(c02e8fa0,c010169e,c062a200,0,c041ab58) at panic+0x123
pmap_change_attrs(c04995ec,0,40,283) at pmap_change_attrs+0xd5
genfs_putpages(cb033d40,0,cb033d58,c36aa640,0) at genfs_putpages+0x43f
VOP_PUTPAGES(cb1e93f8,0,0,0,0,11,0,0) at VOP_PUTPAGES+0x49
ffs_full_fsync(cb033e58,cb1e93f8,c0682000,c0163a56,0) at ffs_full_fsync+0x89
ffs_fsync(cb033e58,10012,c0642840,cb033e48,cb1e93f8) at ffs_fsync+0x3c
VOP_FSYNC(cb1e93f8,c05ebe80,0,0,0,0,0,cb034004) at VOP_FSYNC+0x58
ffs_sync(c0659600,3,c05ebe80,cb034004) at ffs_sync+0xcf
sync_fsync(cb033f28,0,cb033f2c,c0165e2f,ffffffff) at sync_fsync+0x5c
VOP_FSYNC(cb0e573c,c05ebe80,8,0,0,0,0,cb034004) at VOP_FSYNC+0x58
sched_sync(cb034004) at sched_sync+0xb1
End traceback...