Peterson's solution to the critical section problem, is not guaranteed on modern architecture why?

Question

The Peterson's solution to the critical section problem,

Init: flag[2]={False}  //two process problem
Init turn=i or j.
do {
flag [i] = TRUE;
turn= j;
while (flag[j] && turn==j);
critical section
 flag [i] = FALSE; 
remainder section
} while (TRUE);

hence there is no guarantee that this algorithm will work efficiently on Modern Architecture systems.(Ref:- Galvin Book Page No - 229 ), Why so, can somebody help me out?

Comments

Looks I have not understood the complete context, ie what is the problem what is the doubt. I hope you are talking about http://en.wikipedia.org/wiki/Peterson%27s_algorithm which has limitation on more then one CPU architecture, and works perfectly only on single CPU architecture which keep sequential operations intact.

Sorry I have not understood the code segment which you provided.

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yeah as per wikipedia...you may refer the book as per reference given... it is software solution, problem of multiple processor generally comes into hardware solutions(As same wikipedia page says below in Notes).

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So what is the question? can you please elaborate?