Do not dereference vp->v_rdev without holding any of dev_mtx or vnode lock. Use code similar to devfs_fp_check(), but inlined to feet other checks performed by ttyhook_register().
Do not dereference vp->v_rdev without holding any of dev_mtx or vnode
lock. Use code similar to devfs_fp_check(), but inlined to feet other
checks performed by ttyhook_register().

Reviewed by:	ed

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