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I would like to know why preemption does not solve priority inversion problem?
If we have preemptive kernel. Then why priority inversion problem does not get solved?
Ok, let’s say we have two processes. Let’s also assume that the process which has lower priority gets a lock. When the higher-priority process becomes ready, it preempts the other process. If the higher-priority process needs that lock, it can’t get it due to the other process which has lower priority. That means, lower-priority process blocks the higher-priority one. It prevents higher-priority process from running. This is called “Priority Inversion”.
Obviously, preemption is not a solution for priority inversion. The solution is “Priority Inheritance”. It means that we should temporarily increase the process’s priority whenever it acquires a lock that is also needed by a higher-priority process. It should be the highest-priority process among the other processes which might want the same lock.