防止死锁和避免死锁之间的区别

1.防止死锁：
防止死锁是指阻止发生死锁所需的至少四个条件之一。如果我们能够阻止其中任何一个，那么可以避免死锁。

需要阻止的四个条件是：

1. 互斥
2. 保持并等待
3. 无抢占
4. 循环等待

假脱机和非阻塞同步算法用于防止上述情况。在死锁预防中，所有请求都在有限的时间内被授予。

2.避免死锁：
在避免死锁中，我们必须在死锁真正发生之前就进行预测，并确保系统不会进入不安全状态。如果仔细分配资源，可以避免死锁。为了避免死锁，我们使用银行家和安全算法进行资源分配。在避免死锁的情况下，在流程开始时会说明每种类型将需要的最大资源数量。

防止死锁和避免死锁的区别：

S.NO.	Factors	Deadlock Prevention	Deadlock Avoidance
1.	Concept	It blocks at least one of the conditions necessary for deadlock to occur.	It ensures that system does not go in unsafe state
2.	Resource Request	All the resources are requested together.	Resource requests are done according to the available safe path.
3.	Information required	It does not requires information about existing resources, available resources and resource requests	It requires information about existing resources, available resources and resource requests
4.	Procedure	It prevents deadlock by constraining resource request process and handling of resources.	It automatically considers requests and check whether it is safe for system or not.
5.	Preemption	Sometimes, preemption occurs more frequently.	In deadlock avoidance there is no preemption.
6.	Resource allocation strategy	Resource allocation strategy for deadlock prevention is conservative.	Resource allocation strategy for deadlock prevention is not conservative.
7.	Future resource requests	It doesn’t requires knowledge of future process resource requests.	It requires knowledge of future process resource requests.
8.	Advantage	It doesn’t have any cost involved because it has to just make one of the conditions false so that deadlock doesn’t occur.	There is no system under-utilization as this method works dynamically to allocate the resuorces.
9.	Disadvantage	Deadlock prevention has low device utilization.	Deadlock avoidance can block processes for too long.
10.	Example	Spooling and non-blocking synchronization algorithms are used.	Banker’s and safety algorithm is used.