Link to Mutex poisoning docs from RwLock docs

Author: purplesyringa

library/std/src/sync/poison/rwlock.rs

@@ -46,11 +46,13 @@ use crate::sys::sync as sys;
 ///
 /// # Poisoning
 ///
-/// An `RwLock`, like [`Mutex`], will usually become poisoned on a panic. Note,
+/// An `RwLock`, like [`Mutex`], will [usually] become poisoned on a panic. Note,
 /// however, that an `RwLock` may only be poisoned if a panic occurs while it is
 /// locked exclusively (write mode). If a panic occurs in any reader, then the
 /// lock will not be poisoned.
 ///
+/// [usually]: super::Mutex#poisoning
+///
 /// # Examples
 ///
 /// ```