Synchronization mechanism doubt

Question

I read that one of the disadvantage of busy waiting solution to synchronization is that PRIORITY INVERSION can occur in it.

My doubt is, does the priority inversion problem only occur in busy waiting solution or it can occur in without busy waiting solution too. Please explain. Thanks.

Answer 1

yes you are talking abut non-busy waiting means of SEMAPHORE..yes problem of priority inversion occure here too...

say when you are using Binary semaphore ...now assume a process comes and do DOWN() on semaphore ....and enter into CS..but as same time a high priority process comes...

 if hight priority process leads low priority too preempt...then process inside CS will not do UP on semaphore and result is that no one can enter into CS....as logically low priority is still holding CS....hence priority inversion occure.....

but to cause PRIORITY INVERSION...PROCESS MUST BE PREEMPTED before executing UP() on mutex..

Comments

Thanks...

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Priority inversion will not occur in Without busy waiting solution.

If higher priority process came and it failed to perform down on semaphore than the process will be blocked and the lower priority process can complete its CS and and perform UP on semaphore and WAKEUP Higher priority process.