From 2e1b4f512d4abe0817222fbc839187448860fbf6 Mon Sep 17 00:00:00 2001
From: daan <daanl@outlook.com>
Date: Wed, 22 Jul 2020 13:45:04 -0700
Subject: [PATCH] make max update in the stats atomic

---
 include/mimalloc-atomic.h | 26 ++++++++++++++++++++++----
 src/stats.c               |  2 +-
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/include/mimalloc-atomic.h b/include/mimalloc-atomic.h
index 8577dbc5..a0452f5c 100644
--- a/include/mimalloc-atomic.h
+++ b/include/mimalloc-atomic.h
@@ -27,10 +27,6 @@ terms of the MIT license. A copy of the license can be found in the file
 // Atomic operations specialized for mimalloc
 // ------------------------------------------------------
 
-// Atomically add 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_addi64(volatile int64_t* p, int64_t add);
-
 // Atomically add a value; returns the previous value. Memory ordering is relaxed.
 static inline uintptr_t mi_atomic_add(volatile _Atomic(uintptr_t)* p, uintptr_t add);
 
@@ -65,6 +61,14 @@ static inline void mi_atomic_write(volatile _Atomic(uintptr_t)* p, uintptr_t x);
 // Yield
 static inline void mi_atomic_yield(void);
 
+// Atomically add 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_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.
+static inline void mi_atomic_maxi64(volatile int64_t* p, int64_t x);
+
 
 // Atomically subtract a value; returns the previous value.
 static inline uintptr_t mi_atomic_sub(volatile _Atomic(uintptr_t)* p, uintptr_t sub) {
@@ -177,6 +181,13 @@ static inline void mi_atomic_addi64(volatile _Atomic(int64_t)* p, int64_t add) {
   #endif
 }
 
+static inline void mi_atomic_maxi64(volatile _Atomic(int64_t)*p, int64_t x) {
+  int64_t current;
+  do {
+    current = *p;
+  } while (current < x && _InterlockedCompareExchange64(p, x, current) != current);
+}
+
 #else
 #ifdef __cplusplus
 #define  MI_USING_STD   using namespace std;
@@ -187,6 +198,13 @@ 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);
diff --git a/src/stats.c b/src/stats.c
index e0c7f01a..06858d1c 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);
-    if (stat->current > stat->peak) stat->peak = stat->current;  // racing.. it's ok
+    mi_atomic_maxi64(&stat->peak, stat->current);
     if (amount > 0) {
       mi_atomic_addi64(&stat->allocated,amount);
     }