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Info
Reading the docs here Atomics - The Rustonomicon
When thread A releases a location in memory and then thread B subsequently acquires the same location in memory, causality is established. Every write (including non-atomic and relaxed atomic writes) that **happened before** A's release will be observed by B after its acquisition. However no causality is established with any other threads. Similarly, no causality is established if A and B access different locations in memory.
Here what does "happened before" A for a non-atomic write precisely mean?
Will any write appearing before in the code qualify, or is some logical causality required?
// thread 1
let my_ptr: *mut usize = //...
std::ptr::write(my_ptr, 5); // C
shared_atomic_ptr.store(my_ptr, Ordering::Release); // A
// thread 2
let my_ptr: *const = shared_atomic_ptr.load(my_ptr, Ordering::Acquire); // B
let val = unsafe { std::ptr::read(my_ptr) };
Assuming that in B, we read the value from A's write;
are we guaranteed that val will be 5, or is it possible for the write C to be reordered after A?
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