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/*-------------------------------------------------------------------------
*
* latch.h
* Routines for interprocess latches
*
*
* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/latch.h
*
*-------------------------------------------------------------------------
*/
#ifndef LATCH_H
#define LATCH_H
#include <signal.h>
/*
* Latch structure should be treated as opaque and only accessed through
* the public functions. It is defined here to allow embedding Latches as
* part of bigger structs.
*/
typedef struct
{
sig_atomic_t is_set;
bool is_shared;
int owner_pid;
#ifdef WIN32
HANDLE event;
#endif
} Latch;
/* Bitmasks for events that may wake-up WaitLatch() clients */
#define WL_LATCH_SET (1 << 0)
#define WL_SOCKET_READABLE (1 << 1)
#define WL_SOCKET_WRITEABLE (1 << 2)
#define WL_TIMEOUT (1 << 3)
#define WL_POSTMASTER_DEATH (1 << 4)
/*
* prototypes for functions in latch.c
*/
extern void InitLatch(volatile Latch *latch);
extern void InitSharedLatch(volatile Latch *latch);
extern void OwnLatch(volatile Latch *latch);
extern void DisownLatch(volatile Latch *latch);
extern int WaitLatch(volatile Latch *latch, int wakeEvents, long timeout);
extern int WaitLatchOrSocket(volatile Latch *latch, int wakeEvents,
pgsocket sock, long timeout);
extern void SetLatch(volatile Latch *latch);
extern void ResetLatch(volatile Latch *latch);
#define TestLatch(latch) (((volatile Latch *) latch)->is_set)
/*
* Unix implementation uses SIGUSR1 for inter-process signaling, Win32 doesn't
* need this.
*/
#ifndef WIN32
extern void latch_sigusr1_handler(void);
#else
#define latch_sigusr1_handler()
#endif
#endif /* LATCH_H */
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