C11 Atomics

_Atomic(...) wrapper

• Can wrap most basic types and they become atomic
• Operations become sequentially consistent

atomic_flag

• Atomic boolean value without support for loads or stores
• Can do atomic_flag_test_and_set and atomic_flag_clear
• Must be lock-free
  • Cannot be pre-emption in the middle of instruction

Memory Ordering

1. memory_order_relaxed: no specific memory ordering required
2. memory_order_consume: slightly relaxed version of acquire
3. memory_order_acquire: reads and writes that happen after a lock cannot be moved before it
4. memory_order_release: All writes must be completed before release the lock, cannot be moved after
5. memory_oreder_acq_rel: Combination of 4 and 5
6. memory_order_seq_cst: Full Sequential Consistency