This section of code is something that I wrote to provide mutual exclusion between two

threads. $($Sorry about the formatting $-$ it's Canvas.$)$ Comments?

bool blocked$[2]$;

void thread$($ int id $)$

$\{$

int other $=(id==0)?1$:$0$;

while $($ true$)$

$\{$

while $($ blocked$[$ other $])$ ;$//$ wait in while loop

blocked$[$ id $]=$ true;

$//$ critical section here, then...

blocked$[$ id $]=$ false;

$//$ other code here...

$\}$

$\}$

As long as blocked$[$id$]$ is initialized to false $($for both$)$ it is fine.

Of course it works, this is really the code for a spin$-$loop or like a test$-$and$-$set.

It does not work. Between falling out of the inside while loop and entering the section, the other

thread could also enter.