1 files changed, 174 insertions, 0 deletions
diff --git a/storage/innobase/include/transactional_lock_guard.h b/storage/innobase/include/transactional_lock_guard.h
new file mode 100644
index 00000000..168a6897
--- /dev/null
+++ b/storage/innobase/include/transactional_lock_guard.h
@@ -0,0 +1,174 @@
+/*****************************************************************************
+
+Copyright (c) 2021, MariaDB Corporation.
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+
+*****************************************************************************/
+
+#pragma once
+
+#if defined __powerpc64__
+#elif defined __s390__
+#elif defined _MSC_VER && (defined _M_IX86 || defined _M_X64) && !defined(__clang__)
+#elif defined __GNUC__ && (defined __i386__ || defined __x86_64__)
+# if __GNUC__ >= 8
+# elif defined __clang_major__ && __clang_major__ > 6
+# else
+#  define NO_ELISION
+# endif
+#else /* Transactional memory has not been implemented for this ISA */
+# define NO_ELISION
+#endif
+
+#ifdef NO_ELISION
+constexpr bool have_transactional_memory= false;
+# ifdef UNIV_DEBUG
+static inline bool xtest() { return false; }
+# endif
+# define TRANSACTIONAL_TARGET /* nothing */
+# define TRANSACTIONAL_INLINE /* nothing */
+#else
+# if defined __i386__||defined __x86_64__||defined _M_IX86||defined _M_X64
+extern bool have_transactional_memory;
+bool transactional_lock_enabled();
+
+#  include <immintrin.h>
+#  if defined __GNUC__ && !defined __INTEL_COMPILER
+#   define TRANSACTIONAL_TARGET __attribute__((target("rtm"),hot))
+#   define TRANSACTIONAL_INLINE __attribute__((target("rtm"),hot,always_inline))
+#  else
+#   define TRANSACTIONAL_TARGET /* nothing */
+#   define TRANSACTIONAL_INLINE /* nothing */
+#  endif
+
+TRANSACTIONAL_INLINE static inline bool xbegin()
+{
+  return have_transactional_memory && _xbegin() == _XBEGIN_STARTED;
+}
+
+#  ifdef UNIV_DEBUG
+#   ifdef __GNUC__
+/** @return whether a memory transaction is active */
+bool xtest();
+#   else
+static inline bool xtest() { return have_transactional_memory && _xtest(); }
+#   endif
+#  endif
+
+TRANSACTIONAL_INLINE static inline void xabort() { _xabort(0); }
+
+TRANSACTIONAL_INLINE static inline void xend() { _xend(); }
+# elif defined __powerpc64__ || defined __s390__
+extern bool have_transactional_memory;
+bool transactional_lock_enabled();
+#   define TRANSACTIONAL_TARGET __attribute__((hot))
+#   define TRANSACTIONAL_INLINE __attribute__((hot,always_inline))
+
+/**
+  Newer gcc compilers only provide __builtin_{htm}
+  functions when the -mhtm CFLAG is actually provided. So
+  we've got the option of including it globally, or
+  pushing down the inclusion of htmxlintrin.h to one
+  file with -mhtm enabled and removing the inline
+  optimization.
+
+  Per FIXME in s390x's htmxlintrin.h, the __TM_simple_begin
+  isn't always_inline resulting in duplicate definitions if
+  it where included more than once.  While xabort and xend
+  could be implemented here, we keep the implementation the
+  same as ppc64.
+ */
+TRANSACTIONAL_TARGET bool xbegin();
+TRANSACTIONAL_TARGET void xabort();
+TRANSACTIONAL_TARGET void xend();
+#  ifdef UNIV_DEBUG
+bool xtest();
+#  endif
+
+# endif
+#endif
+
+template<class mutex>
+class transactional_lock_guard
+{
+  mutex &m;
+
+public:
+  TRANSACTIONAL_INLINE transactional_lock_guard(mutex &m) : m(m)
+  {
+#ifndef NO_ELISION
+    if (xbegin())
+    {
+      if (was_elided())
+        return;
+      xabort();
+    }
+#endif
+    m.lock();
+  }
+  transactional_lock_guard(const transactional_lock_guard &)= delete;
+  TRANSACTIONAL_INLINE ~transactional_lock_guard()
+  {
+#ifndef NO_ELISION
+    if (was_elided()) xend(); else
+#endif
+    m.unlock();
+  }
+
+#ifndef NO_ELISION
+  bool was_elided() const noexcept { return !m.is_locked_or_waiting(); }
+#else
+  bool was_elided() const noexcept { return false; }
+#endif
+};
+
+template<class mutex>
+class transactional_shared_lock_guard
+{
+  mutex &m;
+#ifndef NO_ELISION
+  bool elided;
+#else
+  static constexpr bool elided= false;
+#endif
+
+public:
+  TRANSACTIONAL_INLINE transactional_shared_lock_guard(mutex &m) : m(m)
+  {
+#ifndef NO_ELISION
+    if (xbegin())
+    {
+      if (!m.is_write_locked())
+      {
+        elided= true;
+        return;
+      }
+      xabort();
+    }
+    elided= false;
+#endif
+    m.lock_shared();
+  }
+  transactional_shared_lock_guard(const transactional_shared_lock_guard &)=
+    delete;
+  TRANSACTIONAL_INLINE ~transactional_shared_lock_guard()
+  {
+#ifndef NO_ELISION
+    if (was_elided()) xend(); else
+#endif
+    m.unlock_shared();
+  }
+
+  bool was_elided() const noexcept { return elided; }
+};