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*****************************************************************************/

/**************************************************/ /**
 @file include/log0write.h

 *******************************************************/

#ifndef log0write_h
#define log0write_h

#ifndef UNIV_HOTBACKUP

/* std::memory_order_X */
#include <atomic>

/* log.write_to_file_requests_interval */
#include "log0sys.h"

/* log_t&, lsn_t */
#include "log0types.h"

/* srv_threads */
#include "srv0srv.h"

/**************************************************/ /**

 @name Log - waiting for redo written to disk.

 *******************************************************/

/** @{ */

/** Waits until the redo log is written up to a provided lsn.
@param[in]  log             redo log
@param[in]  lsn             lsn to wait for
@param[in]  flush_to_disk   true: wait until it is flushed
@return statistics about waiting inside */
Wait_stats log_write_up_to(log_t &log, lsn_t lsn, bool flush_to_disk);

/** Total number of redo log flushes (fsyncs) that have been started since
the redo log system (log_sys) became initialized (@see log_sys_init).
@return total number of fsyncs or 0 if the redo log system is uninitialized */
uint64_t log_total_flushes();

/** Number of currently pending redo log flushes (fsyncs in-progress).
@return number of pending fsyncs or 0 if the redo log system is uninitialized */
uint64_t log_pending_flushes();

/** Checks if the redo log writer exited extra margin. To minimize flipping
of log.m_writer_inside_extra_margin, the check assumes the very pessimistic
scenario in which a next write of the log_writer thread, would be executed
up to the current lsn.

Requirement: log.writer_mutex acquired and log.m_writer_inside_extra_margin
is true, before calling this function.

@remarks
This method is supposed to be used by the log_checkpointer thread to detect
situation in which the redo log writer has actually exited the extra_margin,
because of advanced log.last_checkpoint_lsn, but the log_writer thread didn't
notice it because it has not been active since then (e.g. because there is
nothing more to write, ie. log.write_lsn == current lsn).

@param[in,out]  log  redo log */
void log_writer_check_if_exited_extra_margin(log_t &log);

/** @} */

/**************************************************/ /**

 @name Log - the log write threads.

 *******************************************************/

/** @{ */

/** Pause / resume the log writer, the log flusher, the log write notifier
and the log flush notifier threads based on innodb_log_writer_threads value.
@note Calls to this function should be protected externally by some mutex.
The caller innodb_log_writer_threads_update() is protected
by LOCK_global_system_variables in mysqld. */
void log_control_writer_threads(log_t &log);

/** The log writer thread routine.
@param[in,out]	log_ptr		pointer to redo log */
void log_writer(log_t *log_ptr);

/** The log flusher thread routine.
@param[in,out]	log_ptr		pointer to redo log */
void log_flusher(log_t *log_ptr);

/** The log flush notifier thread routine.
@param[in,out]	log_ptr		pointer to redo log */
void log_flush_notifier(log_t *log_ptr);

/** The log write notifier thread routine.
@param[in,out]	log_ptr		pointer to redo log */
void log_write_notifier(log_t *log_ptr);

/** Validates that the log writer thread is active.
Used only to assert, that the state is correct. */
void log_writer_thread_active_validate();

/** Validates that the log writer, flusher threads are active.
Used only to assert, that the state is correct.
@param[in]	log	redo log */
void log_background_write_threads_active_validate(const log_t &log);

#define log_flusher_mutex_enter(log) mutex_enter(&((log).flusher_mutex))

#define log_flusher_mutex_enter_nowait(log) \
  mutex_enter_nowait(&((log).flusher_mutex))

#define log_flusher_mutex_exit(log) mutex_exit(&((log).flusher_mutex))

#define log_flusher_mutex_own(log) \
  (mutex_own(&((log).flusher_mutex)) || !log_flusher_is_active())

#define log_flush_notifier_mutex_enter(log) \
  mutex_enter(&((log).flush_notifier_mutex))

#define log_flush_notifier_mutex_exit(log) \
  mutex_exit(&((log).flush_notifier_mutex))

#define log_flush_notifier_mutex_own(log) \
  (mutex_own(&((log).flush_notifier_mutex)) || !log_flush_notifier_is_active())

#define log_writer_mutex_enter(log) mutex_enter(&((log).writer_mutex))

#define log_writer_mutex_enter_nowait(log) \
  mutex_enter_nowait(&((log).writer_mutex))

#define log_writer_mutex_exit(log) mutex_exit(&((log).writer_mutex))

#define log_writer_mutex_own(log) \
  (mutex_own(&((log).writer_mutex)) || !log_writer_is_active())

#define log_write_notifier_mutex_enter(log) \
  mutex_enter(&((log).write_notifier_mutex))

#define log_write_notifier_mutex_exit(log) \
  mutex_exit(&((log).write_notifier_mutex))

#define log_write_notifier_mutex_own(log) \
  (mutex_own(&((log).write_notifier_mutex)) || !log_write_notifier_is_active())

/** Checks if log writer thread is active.
@return true if and only if the log writer thread is active */
inline bool log_writer_is_active() {
  return srv_thread_is_active(srv_threads.m_log_writer);
}

/** Checks if log write notifier thread is active.
@return true if and only if the log write notifier thread is active */
inline bool log_write_notifier_is_active() {
  return srv_thread_is_active(srv_threads.m_log_write_notifier);
}

/** Checks if log flusher thread is active.
@return true if and only if the log flusher thread is active */
inline bool log_flusher_is_active() {
  return srv_thread_is_active(srv_threads.m_log_flusher);
}

/** Checks if log flush notifier thread is active.
@return true if and only if the log flush notifier thread is active */
inline bool log_flush_notifier_is_active() {
  return srv_thread_is_active(srv_threads.m_log_flush_notifier);
}

/** Checks if requests to write redo log buffer to disk are frequent
(which means that there is at least one request per 1ms in average).
@param[in]  interval  how often in average requests happen
@return true iff requests are considered frequent */
inline bool log_write_to_file_requests_are_frequent(
    std::chrono::microseconds interval) {
  return interval < std::chrono::milliseconds{1};
}

/** Checks if requests to write redo log buffer to disk are frequent
(which means that there is at least one request per 1ms in average).
@param[in]  log  redo log
@return true iff requests are considered frequent */
inline bool log_write_to_file_requests_are_frequent(const log_t &log) {
  return log_write_to_file_requests_are_frequent(
      log.write_to_file_requests_interval.load(std::memory_order_relaxed));
}

/** @} */

#else

#define log_writer_mutex_own(log) true

#endif /* UNIV_HOTBACKUP */

#endif /* !log0write_h */