Merge pull request #481 from RalfJung/deliberate-ub

deliberate-ub: mention the load-load races in tokio

Author: RalfJung

Diff for: resources/deliberate-ub.md

@@ -19,6 +19,8 @@ We should evaluate whether there truly is some use-case here that is not current
   see the [discussion here](https://github.com/rust-lang/unsafe-code-guidelines/issues/449).<br>
   The alternative is to not use the "fast path" for problematic types (and fall back to the SeqLock), but that requires some way to query at `const`-time whether the type contains padding (or provenance).
   (Or of course one can use inline assembly, but it would be better if that was not required.)
+* tokio causes race conditions between atomic and non-atomic loads which are [not permitted](https://doc.rust-lang.org/nightly/std/sync/atomic/index.html#memory-model-for-atomic-accesses);
+  see [this issue](https://github.com/tokio-rs/tokio/issues/6155) for details.
 
 ### Cases related to aliasing