codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * condition_variable.h4 *	  Condition variables5 *6 * A condition variable is a method of waiting until a certain condition7 * becomes true.  Conventionally, a condition variable supports three8 * operations: (1) sleep; (2) signal, which wakes up one process sleeping9 * on the condition variable; and (3) broadcast, which wakes up every10 * process sleeping on the condition variable.  In our implementation,11 * condition variables put a process into an interruptible sleep (so it12 * can be canceled prior to the fulfillment of the condition) and do not13 * use pointers internally (so that they are safe to use within DSMs).14 *15 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group16 * Portions Copyright (c) 1994, Regents of the University of California17 *18 * src/include/storage/condition_variable.h19 *20 *-------------------------------------------------------------------------21 */22#ifndef CONDITION_VARIABLE_H23#define CONDITION_VARIABLE_H24 25#include "storage/proclist_types.h"26#include "storage/spin.h"27 28typedef struct29{30	slock_t		mutex;			/* spinlock protecting the wakeup list */31	proclist_head wakeup;		/* list of wake-able processes */32} ConditionVariable;33 34/*35 * Pad a condition variable to a power-of-two size so that an array of36 * condition variables does not cross a cache line boundary.37 */38#define CV_MINIMAL_SIZE		(sizeof(ConditionVariable) <= 16 ? 16 : 32)39typedef union ConditionVariableMinimallyPadded40{41	ConditionVariable cv;42	char		pad[CV_MINIMAL_SIZE];43} ConditionVariableMinimallyPadded;44 45/* Initialize a condition variable. */46extern void ConditionVariableInit(ConditionVariable *cv);47 48/*49 * To sleep on a condition variable, a process should use a loop which first50 * checks the condition, exiting the loop if it is met, and then calls51 * ConditionVariableSleep.  Spurious wakeups are possible, but should be52 * infrequent.  After exiting the loop, ConditionVariableCancelSleep must53 * be called to ensure that the process is no longer in the wait list for54 * the condition variable.55 */56extern void ConditionVariableSleep(ConditionVariable *cv, uint32 wait_event_info);57extern bool ConditionVariableTimedSleep(ConditionVariable *cv, long timeout,58										uint32 wait_event_info);59extern bool ConditionVariableCancelSleep(void);60 61/*62 * Optionally, ConditionVariablePrepareToSleep can be called before entering63 * the test-and-sleep loop described above.  Doing so is more efficient if64 * at least one sleep is needed, whereas not doing so is more efficient when65 * no sleep is needed because the test condition is true the first time.66 */67extern void ConditionVariablePrepareToSleep(ConditionVariable *cv);68 69/* Wake up a single waiter (via signal) or all waiters (via broadcast). */70extern void ConditionVariableSignal(ConditionVariable *cv);71extern void ConditionVariableBroadcast(ConditionVariable *cv);72 73#endif							/* CONDITION_VARIABLE_H */74