About Operating Systems concepts

[Ali Reza]

hi all
i have question about concurrency processing in operating systems concepts
suppose that we have two process A,B that running concurrently in a computer.
we have the following algorithm. (this is for A , for B replace a to b)

:retry
flag[a]=false;
if (flag[b] != false ) goto retry;
flag[a]=true;
if (flag[b] != false ) goto retry;
// critical section
flag[a]=false;

:retry
flag[a]=false;
if (flag[b] != false ) goto retry;
flag[a]=true;
if (flag[b] != false ) goto retry;
// critical section
flag[a]=false;

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we know each ideal algorithm for critical section accessing must have three constraints : 1.mutual exclusion , 2.progress , 3.bounded waiting
my question is: for the above algorithm which of these constrain(s) have?

best regards...

[wysota]

Is this some kind of school task?

[Ali Reza]

yes , this is a university assignment for course OS
i think this algorithm has not "Progress" constraint, but not sure!
by this algorithm the "Mutual Exclusion" has been met.
what about Progress cons. ??
thanks Mr Wysota

[wysota]

I'm sorry, we're not allowed to solve school tasks.

[Ali Reza]

please suppose this is not a school task !
just tell me this algorithm satisfy "Progress" or not ?

thanks Mr Wysota

[iamtechie.ami]

You may also check the video to get basic idea of semaphore and shared resource.

https://www.youtube.com/watch?v=VQFJQJGmixM