[compiler-rt] [asan] Prevent printing invalid parent thread (PR #111916)

[Vitaly Buka via llvm-commits]

https://github.com/vitalybuka updated https://github.com/llvm/llvm-project/pull/111916

>From e953c9311789391eed5cb52fced9e6dee0cef8e1 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka at google.com>
Date: Thu, 10 Oct 2024 16:00:54 -0700
Subject: [PATCH 1/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20in?=
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Created using spr 1.3.4
---
 compiler-rt/lib/asan/asan_descriptions.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/asan/asan_descriptions.cpp b/compiler-rt/lib/asan/asan_descriptions.cpp
index 1c2f20a76343bb..778e134f1cf2a5 100644
--- a/compiler-rt/lib/asan/asan_descriptions.cpp
+++ b/compiler-rt/lib/asan/asan_descriptions.cpp
@@ -63,7 +63,10 @@ void DescribeThread(AsanThreadContext *context) {
   if (flags()->print_full_thread_history) {
     AsanThreadContext *parent_context =
         GetThreadContextByTidLocked(context->parent_tid);
-    DescribeThread(parent_context);
+    // `context->parent_tid` may point to reused slot, double check, `unique_id`
+    // of new user will always be greater then the child.
+    if (context->unique_id > parent_context->unique_id)
+      DescribeThread(parent_context);
   }
 }
 

>From 01ef2eb53019e42e6596de80b3a3df79ed29b6ab Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka at google.com>
Date: Thu, 10 Oct 2024 16:03:46 -0700
Subject: [PATCH 2/2] comment

Created using spr 1.3.4
---
 compiler-rt/lib/asan/asan_descriptions.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_descriptions.cpp b/compiler-rt/lib/asan/asan_descriptions.cpp
index 778e134f1cf2a5..8bbbd47ba15ca1 100644
--- a/compiler-rt/lib/asan/asan_descriptions.cpp
+++ b/compiler-rt/lib/asan/asan_descriptions.cpp
@@ -63,8 +63,8 @@ void DescribeThread(AsanThreadContext *context) {
   if (flags()->print_full_thread_history) {
     AsanThreadContext *parent_context =
         GetThreadContextByTidLocked(context->parent_tid);
-    // `context->parent_tid` may point to reused slot, double check, `unique_id`
-    // of new user will always be greater then the child.
+    // `context->parent_tid` may point to reused slot. Check `unique_id` which
+    // is always smaller for the parent, always greater for a new user.
     if (context->unique_id > parent_context->unique_id)
       DescribeThread(parent_context);
   }