diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 97cc76d833e9e..929441125dd52 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -4,7 +4,7 @@ use std::sync::Arc;
 
 use rustc_hir::attrs::Deprecation;
 use rustc_hir::def::{CtorKind, DefKind};
-use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::bug;
@@ -473,6 +473,9 @@ pub(in crate::rmeta) fn provide(providers: &mut Providers) {
             // This is a rudimentary check that does not catch all cases,
             // just the easiest.
             let mut fallback_map: Vec<(DefId, DefId)> = Default::default();
+            // hidden items never enter the map, so dedup here or every
+            // parent path re-enqueues the whole subtree (#160439)
+            let mut fallback_seen: DefIdSet = Default::default();
 
             // Issue 46112: We want the map to prefer the shortest
             // paths when reporting the path to an item. Therefore we
@@ -534,6 +537,10 @@ pub(in crate::rmeta) fn provide(providers: &mut Providers) {
                         }
                         Entry::Vacant(entry) => {
                             if fallback {
+                                // seen already, skip this parent
+                                if !fallback_seen.insert(def_id) {
+                                    return;
+                                }
                                 // We do all of the same steps to fallback entries as to
                                 // preferred entries, except for recording them in a separate map.
                                 // It is important to not return early in the fallback cases to
diff --git a/tests/run-make/rustdoc/visible-parent-map-hang/dep.rs b/tests/run-make/rustdoc/visible-parent-map-hang/dep.rs
new file mode 100644
index 0000000000000..72dd66370c6fb
--- /dev/null
+++ b/tests/run-make/rustdoc/visible-parent-map-hang/dep.rs
@@ -0,0 +1,437 @@
+#![crate_type = "lib"]
+#![allow(dead_code)]
+
+pub trait Tr {
+    fn x();
+}
+pub trait Tr2 {
+    fn x();
+}
+
+#[doc(hidden)]
+pub mod outer {
+    #[doc(hidden)]
+    pub mod l0 {
+        #[doc(hidden)]
+        pub mod s0 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s1 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s2 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s3 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s4 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s5 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s6 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod s7 {
+            pub use super::l1;
+        }
+        #[doc(hidden)]
+        pub mod l1 {
+            #[doc(hidden)]
+            pub mod s0 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s1 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s2 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s3 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s4 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s5 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s6 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod s7 {
+                pub use super::l2;
+            }
+            #[doc(hidden)]
+            pub mod l2 {
+                #[doc(hidden)]
+                pub mod s0 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s1 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s2 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s3 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s4 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s5 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s6 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod s7 {
+                    pub use super::l3;
+                }
+                #[doc(hidden)]
+                pub mod l3 {
+                    #[doc(hidden)]
+                    pub mod s0 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s1 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s2 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s3 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s4 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s5 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s6 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod s7 {
+                        pub use super::l4;
+                    }
+                    #[doc(hidden)]
+                    pub mod l4 {
+                        #[doc(hidden)]
+                        pub mod s0 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s1 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s2 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s3 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s4 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s5 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s6 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod s7 {
+                            pub use super::l5;
+                        }
+                        #[doc(hidden)]
+                        pub mod l5 {
+                            #[doc(hidden)]
+                            pub mod s0 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s1 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s2 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s3 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s4 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s5 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s6 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod s7 {
+                                pub use super::l6;
+                            }
+                            #[doc(hidden)]
+                            pub mod l6 {
+                                #[doc(hidden)]
+                                pub mod s0 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s1 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s2 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s3 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s4 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s5 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s6 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod s7 {
+                                    pub use super::l7;
+                                }
+                                #[doc(hidden)]
+                                pub mod l7 {
+                                    #[doc(hidden)]
+                                    pub mod s0 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s1 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s2 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s3 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s4 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s5 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s6 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod s7 {
+                                        pub use super::l8;
+                                    }
+                                    #[doc(hidden)]
+                                    pub mod l8 {
+                                        #[doc(hidden)]
+                                        pub mod s0 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s1 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s2 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s3 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s4 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s5 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s6 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod s7 {
+                                            pub use super::l9;
+                                        }
+                                        #[doc(hidden)]
+                                        pub mod l9 {
+                                            #[doc(hidden)]
+                                            pub mod s0 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s1 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s2 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s3 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s4 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s5 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s6 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod s7 {
+                                                pub use super::l10;
+                                            }
+                                            #[doc(hidden)]
+                                            pub mod l10 {
+                                                #[doc(hidden)]
+                                                pub mod s0 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s1 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s2 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s3 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s4 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s5 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s6 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod s7 {
+                                                    pub use super::l11;
+                                                }
+                                                #[doc(hidden)]
+                                                pub mod l11 {
+                                                    #[doc(hidden)]
+                                                    pub mod s0 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s1 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s2 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s3 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s4 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s5 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s6 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod s7 {
+                                                        pub use super::leaf::S;
+                                                    }
+                                                    #[doc(hidden)]
+                                                    pub mod leaf {
+                                                        pub struct S;
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/tests/run-make/rustdoc/visible-parent-map-hang/main.rs b/tests/run-make/rustdoc/visible-parent-map-hang/main.rs
new file mode 100644
index 0000000000000..b866432f611e3
--- /dev/null
+++ b/tests/run-make/rustdoc/visible-parent-map-hang/main.rs
@@ -0,0 +1,24 @@
+// #160439: nested #[doc(hidden)] modules made rustdoc hang here.
+#![crate_type = "lib"]
+
+use std::fmt;
+
+pub use dep::Tr;
+
+pub struct Local;
+impl dep::Tr for Local {
+    fn x() {}
+}
+impl dep::Tr2 for Local {
+    fn x() {}
+}
+impl fmt::Display for Local {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "x")
+    }
+}
+impl Default for Local {
+    fn default() -> Self {
+        Local
+    }
+}
diff --git a/tests/run-make/rustdoc/visible-parent-map-hang/rmake.rs b/tests/run-make/rustdoc/visible-parent-map-hang/rmake.rs
new file mode 100644
index 0000000000000..944da900dbf0d
--- /dev/null
+++ b/tests/run-make/rustdoc/visible-parent-map-hang/rmake.rs
@@ -0,0 +1,33 @@
+// #160439: nested #[doc(hidden)] modules made the visible_parent_map BFS
+// exponential. compiletest has no per-test timeout, so time it here.
+use std::process::{Command, Stdio};
+use std::time::{Duration, Instant};
+
+use run_make_support::{env_var, rust_lib_name, rustc};
+
+fn main() {
+    rustc().input("dep.rs").edition("2021").crate_type("lib").run();
+
+    // the bug made rustdoc hang; kill it if it takes too long
+    let mut child = Command::new(env_var("RUSTDOC"))
+        .args(["--edition", "2021", "--crate-name", "main", "-o", "target"])
+        .arg(format!("--extern=dep={}", rust_lib_name("dep")))
+        .arg("main.rs")
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .spawn()
+        .unwrap();
+
+    let deadline = Instant::now() + Duration::from_secs(60);
+    let status = loop {
+        if let Some(status) = child.try_wait().unwrap() {
+            break status;
+        }
+        if Instant::now() > deadline {
+            child.kill().unwrap();
+            panic!("rustdoc timed out: visible_parent_map regression?");
+        }
+        std::thread::sleep(Duration::from_millis(100));
+    };
+    assert!(status.success());
+}