3 ms·

I'm confused why the description refers to it as a "user level" spinlock. Are there some architectures where exchange is a privileged operation?

• tsu 13y ago
  compare-and-swap instruction itself may not be privileged operation but user space spin-lock seldom work in user-space (it's dangerous at least), because a user thread could be preempted.
  • jacquesm 13y ago
    What's even more dangerous, on a single core machine or one that is lightly loaded without any aggressive contention for the lock it may even seem to be working.
  • michaelmior 13y ago
    Ah yes, good point. I had forgotten about that issue.