Index: src/malloc.c
==================================================================
--- src/malloc.c
+++ src/malloc.c
@@ -374,16 +374,20 @@
       assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
       assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_SCRATCH) );
       sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
       if( sqlite3GlobalConfig.bMemstat ){
         int iSize = sqlite3MallocSize(p);
+#ifndef SQLITE_ATOMIC_STATUS_DOWN
         sqlite3_mutex_enter(mem0.mutex);
+#endif
         sqlite3StatusDown(SQLITE_STATUS_SCRATCH_OVERFLOW, iSize);
         sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, iSize);
         sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
         sqlite3GlobalConfig.m.xFree(p);
+#ifndef SQLITE_ATOMIC_STATUS_DOWN
         sqlite3_mutex_leave(mem0.mutex);
+#endif
       }else{
         sqlite3GlobalConfig.m.xFree(p);
       }
     }
   }
@@ -438,15 +442,19 @@
 void sqlite3_free(void *p){
   if( p==0 ) return;  /* IMP: R-49053-54554 */
   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
   if( sqlite3GlobalConfig.bMemstat ){
+#ifndef SQLITE_ATOMIC_STATUS_DOWN
     sqlite3_mutex_enter(mem0.mutex);
+#endif
     sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, sqlite3MallocSize(p));
     sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
     sqlite3GlobalConfig.m.xFree(p);
+#ifndef SQLITE_ATOMIC_STATUS_DOWN
     sqlite3_mutex_leave(mem0.mutex);
+#endif
   }else{
     sqlite3GlobalConfig.m.xFree(p);
   }
 }
 

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -226,10 +226,19 @@
 #  define SQLITE_NOINLINE  __declspec(noinline)
 #else
 #  define SQLITE_NOINLINE
 #endif
 
+/*
+** The SQLITE_ATOMIC_STATUS_DOWN macro is defined if and only if
+** the sqlite3StatusDown() function is threadsafe.
+*/
+#if !defined(SQLITE_DISABLE_INTRINSIC) \
+    && defined(__GNUC__) && GCC_VERSION>=4004000
+# define SQLITE_ATOMIC_STATUS_DOWN 1
+#endif
+
 /*
 ** Make sure that the compiler intrinsics we desire are enabled when
 ** compiling with an appropriate version of MSVC unless prevented by
 ** the SQLITE_DISABLE_INTRINSIC define.
 */

Index: src/status.c
==================================================================
--- src/status.c
+++ src/status.c
@@ -98,15 +98,20 @@
   }
 }
 void sqlite3StatusDown(int op, int N){
   wsdStatInit;
   assert( N>=0 );
+  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
+#if !defined(SQLITE_DISABLE_INTRINSIC) \
+    && defined(__GNUC__) && GCC_VERSION>=4004000
+  (void)__sync_fetch_and_sub(&wsdStat.nowValue[op], N);
+#else
   assert( op>=0 && op<ArraySize(statMutex) );
   assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
                                            : sqlite3MallocMutex()) );
-  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
   wsdStat.nowValue[op] -= N;
+#endif
 }
 
 /*
 ** Adjust the highwater mark if necessary.
 ** The caller must hold the appropriate mutex.