Witness finds "malloc(M_WAITOK) with non-sleepable lock held" in FreeBSD 7.0-CURRENT (amd64)

I'm developing an Ethernet driver with FreeBSD 7.0-CURRENT (amd64) and
I'm 
receiving many of the following witness errors:

malloc(M_WAITOK) of "128", forcing M_NOWAIT with the following
non-sleepable locks held:
exclusive sleep mutex bce0 (network driver) r = 0 (0xffffffff8111e068)
locked _at_ if_bce.c:4607
KDB: stack backtrace:
kdb_backtrace() at kdb_backtrace+0x37
witness_warn() at witness_warn+0x2c1
uma_zalloc_arg() at uma_zalloc_arg+0x69
malloc() at malloc+0xf5
sysctl_add_oid() at sysctl_add_oid+0xa9
alloc_bounce_zone() at alloc_bounce_zone+0x16b
bus_dma_tag_create() at bus_dma_tag_create+0x1ea
bce_init_rx_chain() at bce_init_rx_chain+0x8e
bce_init_locked() at bce_init_locked+0x1e2
bce_init() at bce_init+0x39
ether_ioctl() at ether_ioctl+0x87
bce_ioctl() at bce_ioctl+0x48e
in6_ifinit() at in6_ifinit+0xbd
in6_update_ifa() at in6_update_ifa+0x563
in6_ifattach_linklocal() at in6_ifattach_linklocal+0x126
in6_ifattach() at in6_ifattach+0xdf
in6_if_up() at in6_if_up+0x59
if_route() at if_route+0x8a
if_up() at if_up+0x13
ifhwioctl() at ifhwioctl+0x2f4
ifioctl() at ifioctl+0x10b
soo_ioctl() at soo_ioctl+0x38c
ioctl() at ioctl+0x436
syscall() at syscall+0x350
Xfast_syscall() at Xfast_syscall+0xa8
--- syscall (54, FreeBSD ELF64, ioctl), rip = 0x8008219ac, rsp =
0x7fffffffe6b8, rbp = 0x1 ---

The bus_dma_tag_create looks like this:

bus_dma_tag_create(
	sc->parent_tag,		/* parent      */
    	4096,				/* alignment   */
    	0,				/* boundary    */
	BUS_SPACE_MAXADDR,	/* lowaddr     */
	BUS_SPACE_MAX_ADDR,	/* lowaddr     */
	NULL,				/* filter      */
	NULL, 			/* filterarg   */
	4096,				/* maxsize     */
	1, 				/* nsegments   */
	4096,				/* maxsegsize  */
	BUS_DMA_ALLOCNOW, 	/* flags       */
	NULL,				/* lockfunc    */
	NULL,				/* lockarg     */
	&sc->rx_bd_chain_tag));

Am I doing something wrong?  The function bce_init_rx_chain is called
from with
a lock but isn't that normal?

David Christensen