thread_stage_guard.h

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#ifndef THREAD_STAGE_GUARD_H_INCLUDED
#define THREAD_STAGE_GUARD_H_INCLUDED
 
#include "mysql/components/services/bits/psi_stage_bits.h"  // PSI_stage_info
#include "sql/sql_class.h"                                  // THD
 
namespace raii {
 
/// RAII guard that sets a thread stage, and restores the previous
/// stage when going out of scope.
class Thread_stage_guard {
 public:
  Thread_stage_guard() = delete;
 
  /// Set the given stage for the session, and remember the previous
  /// stage in a member variable.
  ///
  /// @param[in,out] thd Session object that should change stage.
  ///
  /// @param new_stage The new stage to use for THD.
  ///
  /// @param func Name of the calling function.
  ///
  /// @param file Filename of the caller.
  ///
  /// @param line Line number of the caller.
  Thread_stage_guard(THD *thd, const PSI_stage_info &new_stage,
                     const char *func, const char *file,
                     const unsigned int line)
      : m_new_stage(new_stage),
        m_thd(thd),
        m_func(func),
        m_file(file),
        m_line(line) {
    thd->enter_stage(&new_stage, &m_old_stage, func, file, line);
  }
 
  Thread_stage_guard(const Thread_stage_guard &) = delete;
  Thread_stage_guard(Thread_stage_guard &&) = delete;
  Thread_stage_guard &operator=(const Thread_stage_guard &) = delete;
  Thread_stage_guard &operator=(Thread_stage_guard &&) = delete;
 
  /// Revert back to the old stage before this object goes out of scope.
  void set_old_stage() const {
    m_thd->enter_stage(&m_old_stage, nullptr, m_func, m_file, m_line);
  }
 
  /// Restore the new stage, in case set_old_stage was used earlier.
  void set_new_stage() const {
    m_thd->enter_stage(&m_new_stage, nullptr, m_func, m_file, m_line);
  }
 
  /// Revert the old stage that was used before this object's
  /// constructor was invoked.
  ///
  /// @note This will set the function/filename/line number relating
  /// to where the Thread_stage_guard was created, not where it went
  /// out of scope.
  ~Thread_stage_guard() { set_old_stage(); }
 
 private:
  /// The previous stage.
  PSI_stage_info m_old_stage;
  /// The new stage.
  PSI_stage_info m_new_stage;
  /// The session.
  THD *m_thd;
  /// The name of the calling function.
  const char *m_func;
  /// The filename of the caller.
  const char *m_file;
  /// The Line number of the caller.
  const unsigned int m_line;
};
 
// NOLINTBEGIN(cppcoreguidelines-macro-usage)
 
/// Set the thread stage for the given thread, and make it restore the
/// previous stage at the end of the invoking scope, using the named
/// local RAII variable.
///
/// @param name A variable name. The macro will define a variable of
/// type Thread_stage_guard with this name in the current scope where
/// this macro is invoked.
///
/// @param thd The thread for which the stage should be set.
///
/// @param new_stage The new stage.  `thd` will use this stage until
/// the end of the scope where the macro is invoked.  At that point,
/// the stage is reverted to what it was before invoking this macro.
#define NAMED_THD_STAGE_GUARD(name, thd, new_stage)  \
  raii::Thread_stage_guard name {                    \
    (thd), (new_stage), __func__, __FILE__, __LINE__ \
  }
 
/// Set the thread stage for the given thread, and make it restore the
/// previous stage at the end of the invoking scope.
///
/// @param thd The thread for which the stage should be set.
///
/// @param new_stage The new stage.  `thd` will use this stage until
/// the end of the scope where the macro is invoked.  At that point,
/// the stage is reverted to what it was before invoking this macro.
#define THD_STAGE_GUARD(thd, new_stage) \
  NAMED_THD_STAGE_GUARD(_thread_stage_guard_##new_stage, (thd), (new_stage))
 
// NOLINTEND(cppcoreguidelines-macro-usage)
 
}  // namespace raii
 
#endif  /// THREAD_STAGE_GUARD_H_INCLUDED