See the stack trace; the details of what happened -- on demand. All the software built, in a regular manner, from the source: --------------------------- 10.1-STABLE #0 r283831: Sun May 31 13:52:02 EDT 2015 --------------------------- Fatal trap 1: privileged instruction fault while in kernel mode cpuid = 0; apic id = 10 instruction pointer = 0x20:0xffffffff8098fa01 stack pointer = 0x28:0xfffffe0113d1b550 frame pointer = 0x28:0xfffffe0113d1b5a0 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 = 2063 (mplayer) trap number = 1 panic: privileged instruction fault cpuid = 0 KDB: stack backtrace: #0 0xffffffff8097cfe0 at kdb_backtrace+0x60 #1 0xffffffff80940869 at vpanic+0x189 #2 0xffffffff809406d3 at panic+0x43 #3 0xffffffff80d3400f at trap_fatal+0x38f #4 0xffffffff80d33c6c at trap+0x75c #5 0xffffffff80d196a2 at calltrap+0x8 #6 0xffffffff81accb70 at dmu_read_uio_dnode+0xa0 #7 0xffffffff81accaa4 at dmu_read_uio_dbuf+0x34 #8 0xffffffff81b639a3 at zfs_freebsd_read+0x3e3 #9 0xffffffff80e5adb1 at VOP_READ_APV+0xa1 #10 0xffffffff809f3975 at vn_read+0x165 #11 0xffffffff809eff1b at vn_io_fault+0x10b #12 0xffffffff809944d5 at dofileread+0x95 #13 0xffffffff809941f8 at kern_readv+0x68 #14 0xffffffff80994183 at sys_read+0x63 #15 0xffffffff80d34927 at amd64_syscall+0x357 #16 0xffffffff80d1998b at Xfast_syscall+0xfb Uptime: 3h39m2s #0 doadump (textdump=<value optimized out>) at pcpu.h:219 219 __asm("movq %%gs:%1,%0" : "=r" (td) (kgdb) bt #0 doadump (textdump=<value optimized out>) at pcpu.h:219 #1 0xffffffff80940462 in kern_reboot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:451 #2 0xffffffff809408a8 in vpanic (fmt=<value optimized out>, ap=<value optimized out>) at /usr/src/sys/kern/kern_shutdown.c:758 #3 0xffffffff809406d3 in panic (fmt=0x0) at /usr/src/sys/kern/kern_shutdown.c:687 #4 0xffffffff80d3400f in trap_fatal (frame=<value optimized out>, eva=<value optimized out>) at /usr/src/sys/amd64/amd64/trap.c:857 #5 0xffffffff80d33c6c in trap (frame=<value optimized out>) at /usr/src/sys/amd64/amd64/trap.c:203 #6 0xffffffff80d196a2 in calltrap () at /usr/src/sys/amd64/amd64/exception.S:236 #7 0xffffffff8098fa01 in uiomove_faultflag (cp=0xfffff80019005600, n=319, uio=0xfffffe0113d1b8e0, nofault=<value optimized out>) at proc.h:983 #8 0xffffffff81accb70 in dmu_read_uio_dnode () from /boot/kernel/zfs.ko #9 0xffffffff81accaa4 in dmu_read_uio_dbuf () from /boot/kernel/zfs.ko #10 0xffffffff81b639a3 in zfs_freebsd_read () from /boot/kernel/zfs.ko #11 0xffffffff80e5adb1 in VOP_READ_APV (vop=<value optimized out>, a=<value optimized out>) at vnode_if.c:932 #12 0xffffffff809f3975 in vn_read (fp=0xfffff8001915e910, uio=0xfffffe0113d1b8e0, active_cred=<value optimized out>, flags=<value optimized out>, td=0x2d) at vnode_if.h:384 #13 0xffffffff809eff1b in vn_io_fault (fp=0xfffff8001915e910, uio=0xfffffe0113d1b8e0, active_cred=0xfffffe0113d1b8e0, flags=0, td=0x2d) at /usr/src/sys/kern/vfs_vnops.c:1159 #14 0xffffffff809944d5 in dofileread (td=0xfffff8001748f490, fd=5, fp=0xfffff8001915e910, auio=0xfffffe0113d1b8e0, offset=<value optimized out>, flags=0) at file.h:296 #15 0xffffffff809941f8 in kern_readv (td=0xfffff8001748f490, fd=5, auio=0xfffffe0113d1b8e0) at /usr/src/sys/kern/sys_generic.c:270 #16 0xffffffff80994183 in sys_read (td=<value optimized out>, uap=<value optimized out>) at /usr/src/sys/kern/sys_generic.c:185 #17 0xffffffff80d34927 in amd64_syscall (td=0xfffff8001748f490, traced=0) at subr_syscall.c:134 #18 0xffffffff80d1998b in Xfast_syscall () at /usr/src/sys/amd64/amd64/exception.S:396 #19 0x00000008074abe8a in ?? () Previous frame inner to this frame (corrupt stack?) Cu