1 files changed, 49 insertions, 1 deletions
diff --git a/storage/innobase/include/srw_lock.h b/storage/innobase/include/srw_lock.h
index 01067322..98c256d3 100644
--- a/storage/innobase/include/srw_lock.h
+++ b/storage/innobase/include/srw_lock.h
@@ -153,7 +153,7 @@ template<bool spinloop> class srw_lock_impl;
 
 /** Slim shared-update-exclusive lock with no recursion */
 template<bool spinloop>
-class ssux_lock_impl final
+class ssux_lock_impl
 {
 #ifdef UNIV_PFS_RWLOCK
   friend class ssux_lock;
@@ -550,3 +550,51 @@ typedef srw_lock_impl<false> srw_lock;
 typedef srw_lock_impl<true> srw_spin_lock;
 
 #endif
+
+#ifdef UNIV_DEBUG
+# include <unordered_set>
+
+class srw_lock_debug : private srw_lock
+{
+  /** The owner of the exclusive lock (0 if none) */
+  std::atomic<pthread_t> writer;
+  /** Protects readers */
+  mutable srw_mutex readers_lock;
+  /** Threads that hold the lock in shared mode */
+  std::atomic<std::unordered_multiset<pthread_t>*> readers;
+
+  /** Register a read lock. */
+  void readers_register();
+
+public:
+  void SRW_LOCK_INIT(mysql_pfs_key_t key);
+  void destroy();
+
+#ifndef SUX_LOCK_GENERIC
+  /** @return whether any lock may be held by any thread */
+  bool is_locked_or_waiting() const noexcept
+  { return srw_lock::is_locked_or_waiting(); }
+  /** @return whether an exclusive lock may be held by any thread */
+  bool is_write_locked() const noexcept { return srw_lock::is_write_locked(); }
+#endif
+
+  /** Acquire an exclusive lock */
+  void wr_lock(SRW_LOCK_ARGS(const char *file, unsigned line));
+  /** @return whether an exclusive lock was acquired */
+  bool wr_lock_try();
+  /** Release after wr_lock() */
+  void wr_unlock();
+  /** Acquire a shared lock */
+  void rd_lock(SRW_LOCK_ARGS(const char *file, unsigned line));
+  /** @return whether a shared lock was acquired */
+  bool rd_lock_try();
+  /** Release after rd_lock() */
+  void rd_unlock();
+  /** @return whether this thread is between rd_lock() and rd_unlock() */
+  bool have_rd() const noexcept;
+  /** @return whether this thread is between wr_lock() and wr_unlock() */
+  bool have_wr() const noexcept;
+  /** @return whether this thread is holding rd_lock() or wr_lock() */
+  bool have_any() const noexcept;
+};
+#endif