Database 2PL protocol

Question

In 2PL protocol if all exclusive locks  are acquired by transaction in increasing order of their accesses then is the 2PL starvation free ?

Comments

i have already explained conservative 2PL above but let's take this in depth.

Let's say all locks are acquired by T1 initially, then T2 has to starve until T1 unlocks. and if some operation of T1 is taking too much time then T2 will surely starve.

T1                                    T2

L_X(A)

L_X(B)

 

Execution A  

                          

                               Now here B is taking too much time,

                               Hence T2 has to wait until execution of B

                              Then only T2 can aquire its locks and start its execution.

 

execution of B

                

Hence here Though lock on B in T1 is taken initially but B is taking too much time in T1 hence T2 has to  starve untill T1 unlocks B. Because In T2 also X(A) and X(B) should be acquire at start of its execution

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@Ashwin Kulkarni  so according to this Peterson's solution in OS should be not starvation free because we can't preempt any process while it is executing.

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You're talking about priority inversion problem in Peterson's solution.

Answer 1

It might help
https://gateoverflow.in/102854/2pl-protocol