There has not been any explicit description dealing with deadlock problem in Unix found so far. As we have seen in the section 7.3 of[4] or in the section 6.3 of [5], Unix's main attitude toward deadlock handling is considered to be the Ostrich algorithm, i. e. just ignore it. Ritchie and Thompson [1] said no user-visible lock is provided with the original Unix. The reasons are they are not necessary and insufficient. Although this has not yet been confirmed with published information sources ([11]), Solaris 2 incorporates a deadlock prevention method by breaking the circular wait condition. A hierarchical structure is set on hardware and software interrupts, and higher level events are not allowed to wait for the lower level events. Also the no-preemption condition is broken by having many preemption points in the kernel.