[compiler-rt] [TSan] Increase the number of simultaneously locked mutexes that a thread can hold (PR #116409)

[via llvm-commits]

https://github.com/gbMattN created https://github.com/llvm/llvm-project/pull/116409

I've run into an issue where TSan can't be used on some code without turning off deadlock detection because a thread tries to hold too many mutexes. It would be preferable to be able to use deadlock detection as that is a major benefit of TSan.

Its mentioned in https://github.com/google/sanitizers/issues/950 that the 64 mutex limit was an arbitrary number. I've increased it to 128 and all the tests still pass. Considering the increasing number of cores on CPUs and how programs can now use more threads to take advantage of it, I think raising the limit to 128 would be some good future proofing

>From a2561d5878a02b6955f48a38434c2cc056dd6459 Mon Sep 17 00:00:00 2001
From: gbMattN <matthew.nagy at sony.com>
Date: Fri, 15 Nov 2024 15:41:24 +0000
Subject: [PATCH] [TSan] Increase the limit of simultaniously held mutexes TSan
 can keep track of from 64 to 128

---
 .../sanitizer_deadlock_detector.h             |  2 +-
 compiler-rt/test/tsan/many_held_mutex.cpp     | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 compiler-rt/test/tsan/many_held_mutex.cpp

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_deadlock_detector.h b/compiler-rt/lib/sanitizer_common/sanitizer_deadlock_detector.h
index 0749f633b4bcf5..1664b92b213692 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_deadlock_detector.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_deadlock_detector.h
@@ -120,7 +120,7 @@ class DeadlockDetectorTLS {
     u32 lock;
     u32 stk;
   };
-  LockWithContext all_locks_with_contexts_[64];
+  LockWithContext all_locks_with_contexts_[128];
   uptr n_all_locks_;
 };
 
diff --git a/compiler-rt/test/tsan/many_held_mutex.cpp b/compiler-rt/test/tsan/many_held_mutex.cpp
new file mode 100644
index 00000000000000..479aa20a7b9df3
--- /dev/null
+++ b/compiler-rt/test/tsan/many_held_mutex.cpp
@@ -0,0 +1,23 @@
+// RUN: %clangxx_tsan %s -fsanitize=thread -o %t && %run %t 2>&1 | Filecheck %s
+
+#include <mutex>
+#include <stdio.h>
+
+int main(){
+    const unsigned short NUM_OF_MTX = 128;
+    std::mutex mutexes[NUM_OF_MTX];
+
+    for(int i = 0; i < NUM_OF_MTX; i++){
+        mutexes[i].lock();
+    }
+    for(int i = 0; i < NUM_OF_MTX; i++){
+        mutexes[i].unlock();
+    }
+
+    printf("Success\n");
+
+    return 0;
+}
+
+// CHECK: Success
+// CHECK-NOT: ThreadSanitizer: CHECK failed