Problem regarding mutual exclusion

Question

Process P1	Process P2
P(S1)	P(S1)
P(S2)	P(S2)
Critical Section	Critical Section
V(S2)	V(S1)
V(S1)	V(S2)

In one of the Gateoverflow tests, this question was given and it was told that in the above case mutual exclusion is not guaranteed. But I can't understand why. As far as I see it, when any process accesses the Critical Section, both Semaphore S1 and S2 must be locked. When even one lock could suffice, here both are locked before accessing the critical section. As far as the order of unlocking, I dont see a problem there. Can someone please explain why mutual exclusion is not guaranteed?

Comments

This satisfy mutual exclusion.

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Surely satisfies ME !

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It is depend on types of semaphores and their value

If semaphores are binary then definitely ME

But in case of counter semaphore depend on the initial value.

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if binary semaphore then it will definitely satisfy  ME

but suppose its counting semaphore and both S1 and S2 are some positive values

example

S1=10 and S2=10

then after executing the process p1

preemption after P(S2)

then we can easily enter process P2 since S1=9 and S2=9 

so here mutual exclusion does not satisfy

Answer 1

What is the type of semaphore s1 and s2 here???

Also provide initial values then only we can identify me is guaranteed or not