/*-------------------------------------------------------------------------
 * wait_event.h
 *	  Definitions related to wait event reporting
 *
 * Copyright (c) 2001-2024, PostgreSQL Global Development Group
 *
 * src/include/utils/wait_event.h
 * ----------
 */
#ifndef WAIT_EVENT_H
#define WAIT_EVENT_H


/* ----------
 * Wait Classes
 * ----------
 */
#define PG_WAIT_LWLOCK				0x01000000U
#define PG_WAIT_LOCK				0x03000000U
#define PG_WAIT_BUFFERPIN			0x04000000U
#define PG_WAIT_ACTIVITY			0x05000000U
#define PG_WAIT_CLIENT				0x06000000U
#define PG_WAIT_EXTENSION			0x07000000U
#define PG_WAIT_IPC					0x08000000U
#define PG_WAIT_TIMEOUT				0x09000000U
#define PG_WAIT_IO					0x0A000000U

/* enums for wait events */
#include "utils/wait_event_types.h"

extern const char *pgstat_get_wait_event(uint32 wait_event_info);
extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
static inline void pgstat_report_wait_start(uint32 wait_event_info);
static inline void pgstat_report_wait_end(void);
extern void pgstat_set_wait_event_storage(uint32 *wait_event_info);
extern void pgstat_reset_wait_event_storage(void);

extern PGDLLIMPORT uint32 *my_wait_event_info;


/* ----------
 * Wait Events - Extension
 *
 * Use this category when the server process is waiting for some condition
 * defined by an extension module.
 *
 * Extensions can define their own wait events in this category.  They should
 * call WaitEventExtensionNew() with a wait event string.  If the wait event
 * associated to a string is already allocated, it returns the wait event
 * information to use.  If not, it gets one wait event ID allocated from
 * a shared counter, associates the string to the ID in the shared dynamic
 * hash and returns the wait event information.
 *
 * The ID retrieved can be used with pgstat_report_wait_start() or equivalent.
 */
typedef enum
{
	WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION,
	WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED,
} WaitEventExtension;

extern void WaitEventExtensionShmemInit(void);
extern Size WaitEventExtensionShmemSize(void);

extern uint32 WaitEventExtensionNew(const char *wait_event_name);
extern char **GetWaitEventExtensionNames(int *nwaitevents);

/* ----------
 * pgstat_report_wait_start() -
 *
 *	Called from places where server process needs to wait.  This is called
 *	to report wait event information.  The wait information is stored
 *	as 4-bytes where first byte represents the wait event class (type of
 *	wait, for different types of wait, refer WaitClass) and the next
 *	3-bytes represent the actual wait event.  Currently 2-bytes are used
 *	for wait event which is sufficient for current usage, 1-byte is
 *	reserved for future usage.
 *
 *	Historically we used to make this reporting conditional on
 *	pgstat_track_activities, but the check for that seems to add more cost
 *	than it saves.
 *
 *	my_wait_event_info initially points to local memory, making it safe to
 *	call this before MyProc has been initialized.
 * ----------
 */
static inline void
pgstat_report_wait_start(uint32 wait_event_info)
{
	/*
	 * Since this is a four-byte field which is always read and written as
	 * four-bytes, updates are atomic.
	 */
	*(volatile uint32 *) my_wait_event_info = wait_event_info;
}

/* ----------
 * pgstat_report_wait_end() -
 *
 *	Called to report end of a wait.
 * ----------
 */
static inline void
pgstat_report_wait_end(void)
{
	/* see pgstat_report_wait_start() */
	*(volatile uint32 *) my_wait_event_info = 0;
}


#endif							/* WAIT_EVENT_H */