lock_caller may not return immediately

[MoonStar2n]

lock is used very frequently in OPAL, and code should not block in OPAL.

However, in the lock_caller function, if cpu not get lock, it will execute the following try to lock code which is in for loop until it get the lock. I think this design may consume too much time in some scenario, OPAL should return immediately whether or not the lock is acquired.
Looking forward for your answer, thanks.