wait_event.h

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/*-------------------------------------------------------------------------
 * wait_event.h
 *    Definitions related to wait event reporting
 *
 * Copyright (c) 2001-2025, PostgreSQL Global Development Group
 *
 * src/include/utils/wait_event.h
 * ----------
 */
#ifndef WAIT_EVENT_H
#define WAIT_EVENT_H
 
/* 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, InjectionPoint
 *
 * Use InjectionPoint when the server process is waiting in an injection
 * point.  Use Extension for other cases of the server process waiting for
 * some condition defined by an extension module.
 *
 * Extensions can define their own wait events in these categories.  They
 * should call one of these functions 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.
 */
extern uint32 WaitEventExtensionNew(const char *wait_event_name);
extern uint32 WaitEventInjectionPointNew(const char *wait_event_name);
 
extern void WaitEventCustomShmemInit(void);
extern Size WaitEventCustomShmemSize(void);
extern char **GetWaitEventCustomNames(uint32 classId, 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 */