I've had a kernel crash with 3 different RC1 kernels. kernel: FreeBSD 11.1-RC1 #71 r313908+b08656c3ba28(releng/11.1): Sun Jul 2 23:15:23 PDT 2017 kernel: FreeBSD 11.1-RC1 #72 r313908+64e0abde4c70(releng/11.1): Mon Jul 3 07:43:42 PDT 2017 kernel: FreeBSD 11.1-RC1 #73 r313908+ff3a058c4f83(releng/11.1): Mon Jul 3 11:56:29 PDT 2017 # kldstat Id Refs Address Size Name 1 42 0xffffffff80200000 1f67128 kernel 2 1 0xffffffff82169000 3161c0 zfs.ko 3 2 0xffffffff82480000 c9e8 opensolaris.ko 4 1 0xffffffff8248d000 21c68 geom_eli.ko 5 1 0xffffffff824af000 bc68 aesni.ko 6 1 0xffffffff824bb000 114f58 nvidia-modeset.ko 7 3 0xffffffff825d0000 ab7f8 linux.ko 8 3 0xffffffff8267c000 ddc0 linux_common.ko 9 2 0xffffffff8268a000 1056708 nvidia.ko 10 1 0xffffffff83821000 3602 ums.ko 11 1 0xffffffff83825000 3c35c linux64.ko 12 1 0xffffffff83862000 eb0d iscsi.ko Excuse human-induced typos in stack-trace: panic: avl_find() succeeded inside avl_add() cpuid=5 KDB: stack backgrace: #0 0xffffffff80aad9c7 at kdb_backtrace+0x67 #1 0xffffffff80a6baa6 at vpanic+0x186 #2 0xffffffff80a6b913 at panic+0x43 #3 0xffffffff82169df4 at avl_add+0x134 #4 0xffffffff821a9bed at dmu_recv_end+0x16d #5 0xffffffff82231e0f at zfs_ioc_recv+0xb1f #6 0xffffffff82233c36 at zfsdev_ioctl+0x6d6 #7 0xffffffff8093ad38 at devfs_ioctl_f+0x128 #8 0xffffffff80ac9315 at kern_ioctl+0x255 #9 0xffffffff80ac904f at sys_ioctl+0x16f #10 0xffffffff80ee0394 at amd64_syscall+0x6c4 #11 0xffffffff80ec35cb at Xfast_syscall+0xfb It is reproducible. Initially saw it with zfs send | zfs recv (kernel #71), reproduced outside of X so I could see the panic, installed kernel #72 to be more current (had it compiled but not installed since I was doing lots of I/O). Didn't happen with zfs send to file, happened on zfs recv from file, grabbed #73 since it looked like it might apply since I have a da* via ISCSI, and can still reproduce the problem.