Add a memory barrier to the mutex initialization logic, try to work around

an issue reported by WebKit.

FossilOrigin-Name: 11a9a786ec06403addb47f5c6fb142b382fae522

5 files changed, 22 insertions, 0 deletions

diff --git a/src/mutex.c b/src/mutex.c
index 64efd3b05..a2e4e6387 100644
--- a/src/mutex.c
+++ b/src/mutex.c
@@ -53,6 +53,7 @@ int sqlite3MutexInit(void){
     pTo->xMutexLeave = pFrom->xMutexLeave;
     pTo->xMutexHeld = pFrom->xMutexHeld;
     pTo->xMutexNotheld = pFrom->xMutexNotheld;
+    sqlite3MemoryBarrier();
     pTo->xMutexAlloc = pFrom->xMutexAlloc;
   }
   rc = sqlite3GlobalConfig.mutex.xMutexInit();
diff --git a/src/mutex.h b/src/mutex.h
index 03eb1faad..8bcf2353f 100644
--- a/src/mutex.h
+++ b/src/mutex.h
@@ -64,6 +64,7 @@
 #define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
 #define sqlite3MutexInit()        SQLITE_OK
 #define sqlite3MutexEnd()
+#define sqlite3MemoryBarrier()    
 #define MUTEX_LOGIC(X)
 #else
 #define MUTEX_LOGIC(X)            X
diff --git a/src/mutex_unix.c b/src/mutex_unix.c
index 0a493fa6a..e181ba5bd 100644
--- a/src/mutex_unix.c
+++ b/src/mutex_unix.c
@@ -81,6 +81,18 @@ static int pthreadMutexNotheld(sqlite3_mutex *p){
 #endif
 
 /*
+** Try to provide a memory barrier operation, needed for initialization only.
+*/
+void sqlite3MemoryBarrier(void){
+#if defined(__GNUC__)
+  __sync_synchronize();
+#endif
+#ifdef SQLITE_MEMORY_BARRIER
+  SQLITE_MEMORY_BARRIER;
+#endif
+}
+
+/*
 ** Initialize and deinitialize the mutex subsystem.
 */
 static int pthreadMutexInit(void){ return SQLITE_OK; }
diff --git a/src/mutex_w32.c b/src/mutex_w32.c
index fc943acaa..9f2fb048f 100644
--- a/src/mutex_w32.c
+++ b/src/mutex_w32.c
@@ -78,6 +78,13 @@ static int winMutexNotheld(sqlite3_mutex *p){
 #endif
 
 /*
+** Try to provide a memory barrier operation, needed for initialization only.
+*/
+void sqlite3MemoryBarrier(void){
+  MemoryBarrier();
+}
+
+/*
 ** Initialize and deinitialize the mutex subsystem.
 */
 static sqlite3_mutex winMutex_staticMutexes[] = {
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 89b3d798f..eeb0b9950 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3191,6 +3191,7 @@ const sqlite3_mem_methods *sqlite3MemGetMemsys5(void);
   sqlite3_mutex *sqlite3MutexAlloc(int);
   int sqlite3MutexInit(void);
   int sqlite3MutexEnd(void);
+  void sqlite3MemoryBarrier(void);
 #endif
 
 sqlite3_int64 sqlite3StatusValue(int);