From 8aa18d3661e73349fa4fee0a647dbe42a66fd5af Mon Sep 17 00:00:00 2001
From: daan <daanl@outlook.com>
Date: Wed, 22 Jul 2020 14:16:18 -0700
Subject: [PATCH] fix TSAN warning for statistics maximum, issue #130

---
 include/mimalloc-atomic.h | 45 ++++++++++++++++++++++++++++-----------
 src/stats.c               |  2 +-
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/include/mimalloc-atomic.h b/include/mimalloc-atomic.h
index ae9fbbdf..b3732e89 100644
--- a/include/mimalloc-atomic.h
+++ b/include/mimalloc-atomic.h
@@ -65,10 +65,13 @@ static inline void mi_atomic_yield(void);
 // Note: not using _Atomic(int64_t) as it is only used for statistics.
 static inline void mi_atomic_addi64(volatile int64_t* p, int64_t add);
 
-// Atomically take the maximum a 64-bit value; returns the previous value.
-// Note: not using _Atomic(int64_t) as it is only used for statistics.
+// Atomically update `*p` with the maximum of `*p` and `x` as a 64-bit value.
+// Returns the previous value. Note: not using _Atomic(int64_t) as it is only used for statistics.
 static inline void mi_atomic_maxi64(volatile int64_t* p, int64_t x);
 
+// Atomically read a 64-bit value
+// Note: not using _Atomic(int64_t) as it is only used for statistics.
+static inline int64_t mi_atomic_readi64(volatile int64_t* p);
 
 // Atomically subtract a value; returns the previous value.
 static inline uintptr_t mi_atomic_sub(volatile _Atomic(uintptr_t)* p, uintptr_t sub) {
@@ -188,23 +191,24 @@ static inline void mi_atomic_maxi64(volatile _Atomic(int64_t)*p, int64_t x) {
   } while (current < x && _InterlockedCompareExchange64(p, x, current) != current);
 }
 
+static inline int64_t mi_atomic_readi64(volatile _Atomic(int64_t)*p) {
+  #ifdef _WIN64
+  return *p;
+  #else
+  int64_t current;
+  do {
+    current = *p;
+  } while (_InterlockedCompareExchange64(p, current, current) != current);
+  return current;
+  #endif
+}
+
 #else
 #ifdef __cplusplus
 #define  MI_USING_STD   using namespace std;
 #else
 #define  MI_USING_STD
 #endif
-static inline void mi_atomic_addi64(volatile int64_t* p, int64_t add) {
-  MI_USING_STD
-  atomic_fetch_add_explicit((volatile _Atomic(int64_t)*)p, add, memory_order_relaxed);
-}
-static inline void mi_atomic_maxi64(volatile int64_t* p, int64_t x) {
-  MI_USING_STD
-  int64_t current;
-  do {
-    current = atomic_load_explicit((volatile _Atomic(int64_t)*)p, memory_order_relaxed);
-  } while (current < x && !atomic_compare_exchange_weak_explicit((volatile _Atomic(int64_t)*)p, &current, x, memory_order_acq_rel, memory_order_relaxed));
-}
 static inline uintptr_t mi_atomic_add(volatile _Atomic(uintptr_t)* p, uintptr_t add) {
   MI_USING_STD
   return atomic_fetch_add_explicit(p, add, memory_order_relaxed);
@@ -241,6 +245,21 @@ static inline void mi_atomic_write(volatile _Atomic(uintptr_t)* p, uintptr_t x)
   MI_USING_STD
   return atomic_store_explicit(p, x, memory_order_release);
 }
+static inline void mi_atomic_addi64(volatile int64_t* p, int64_t add) {
+  MI_USING_STD
+  atomic_fetch_add_explicit((volatile _Atomic(int64_t)*)p, add, memory_order_relaxed);
+}
+static inline int64_t mi_atomic_readi64(volatile int64_t* p) {
+  MI_USING_STD
+  return atomic_load_explicit((volatile _Atomic(int64_t)*) p, memory_order_relaxed);
+}
+static inline void mi_atomic_maxi64(volatile int64_t* p, int64_t x) {
+  MI_USING_STD
+  int64_t current;
+  do {
+    current = mi_atomic_readi64(p);
+  } while (current < x && !atomic_compare_exchange_weak_explicit((volatile _Atomic(int64_t)*)p, &current, x, memory_order_acq_rel, memory_order_relaxed));
+}
 
 #if defined(__cplusplus)
   #include <thread>
diff --git a/src/stats.c b/src/stats.c
index 06858d1c..172a3c0a 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -27,7 +27,7 @@ static void mi_stat_update(mi_stat_count_t* stat, int64_t amount) {
   {
     // add atomically (for abandoned pages)
     mi_atomic_addi64(&stat->current,amount);
-    mi_atomic_maxi64(&stat->peak, stat->current);
+    mi_atomic_maxi64(&stat->peak, mi_atomic_readi64(&stat->current));
     if (amount > 0) {
       mi_atomic_addi64(&stat->allocated,amount);
     }