Merge 10.5 into 10.6

storage/innobase/include/rw_lock.h

@@ -50,9 +50,22 @@ class rw_lock
   static constexpr uint32_t UPDATER= 1U << 29;
 #endif /* SUX_LOCK_GENERIC */
 
+  /** Start waiting for an exclusive lock. */
+  void write_lock_wait_start()
+  {
+#if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
+    static_assert(WRITER_WAITING == 1U << 30, "compatibility");
+    __asm__ __volatile__("lock btsl $30, %0" : "+m" (lock));
+#elif defined _MSC_VER && (defined _M_IX86 || defined _M_IX64)
+    static_assert(WRITER_WAITING == 1U << 30, "compatibility");
+    _interlockedbittestandset(reinterpret_cast<volatile long*>(&lock), 30);
+#else
+    lock.fetch_or(WRITER_WAITING, std::memory_order_relaxed);
+#endif
+  }
   /** Start waiting for an exclusive lock.
   @return current value of the lock word */
-  uint32_t write_lock_wait_start()
+  uint32_t write_lock_wait_start_read()
   { return lock.fetch_or(WRITER_WAITING, std::memory_order_relaxed); }
   /** Wait for an exclusive lock.
   @param l the value of the lock word

storage/innobase/sync/srw_lock.cc

@@ -193,10 +193,10 @@ void ssux_lock_impl<spinloop>::write_lock(bool holding_u)
 {
   for (;;)
   {
-    uint32_t l= write_lock_wait_start();
+    write_lock_wait_start();
 
     const uint32_t e= holding_u ? WRITER_WAITING | UPDATER : WRITER_WAITING;
-    l= e;
+    uint32_t l= e;
     if (write_lock_wait_try(l))
       return;
 
@@ -213,7 +213,7 @@ void ssux_lock_impl<spinloop>::write_lock(bool holding_u)
           return;
       }
 
-      for (l= write_lock_wait_start() | WRITER_WAITING;
+      for (l= write_lock_wait_start_read() | WRITER_WAITING;
            (l | WRITER_WAITING) == e; )
         if (write_lock_wait_try(l))
           return;