Shulou(Shulou.com)06/01 Report--

In order to prevent the occurrence of a deadlock, it is necessary to try to destroy one of the four necessary prerequisites for the occurrence of a deadlock, perhaps allowing a deadlock to occur, but when a deadlock occurs, a deadlock can be detected and the recovery can be completed.

Prevent deadlock

Set certain restrictions to destroy one or more of the four premises where deadlocks occur in order to avoid deadlocks.

Prevent deadlock

In the process of static allocation of capital, there is a way to prevent bits and pieces from entering the insecure form, so as to prevent deadlock.

Detection and release of deadlock

There is no need to take any restrictive measures, the licensing process occurs deadlock in the process of operation. Through the piecemeal detection mechanism, the occurrence of deadlock is detected in real time, and then some way is taken to release the deadlock.

Both the prevention of deadlock and the prevention of deadlock belong to the prevention strategy in advance, but the restriction premise of preventing deadlock is relatively strict, and it is more complex to complete, but it often leads to low effectiveness of piecemeal and low rate of capital application; the restriction premise of preventing deadlock is absolutely loose, and the requirement after capital allocation is determined by algorithm to determine whether it can enter the form of insecurity, which is more complex to complete.

A comparison of several deadlock disposal strategies is shown in Table 2-14.

Table 2-14 comparison of deadlock disposal strategies

-- all kinds of capital allocation strategies can be in the form of secondary advantages, minor defects, deadlock prevention and radical prevention. It is better for capital to be left idle and beg for all capital at once, and capital is deprived of resources. Capital allocation is useful in the process of sudden disposal, and there is no need to stop the low effectiveness of deprivation. The process is extended during initialization; too many times of deprivation. Convenient and sensitive request for new capital deadlock prevention is a tradeoff between "prevention" and "detection" (judging whether it can be deadlocked at operation) to find a safe permission order that does not have to stop stripping and must know the capital requirements in the future. Process can not be blocked for a long time deadlock detection loose, as long as permission to allocate capital current introspection whether the deadlock has occurred during the initialization of the non-extension process, permission to stop the deadlock on-site disposal after deprivation to release the deadlock, cause damage

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