| /*------------------------------------------------------------------------- | |
| * | |
| * condition_variable.h | |
| * Condition variables | |
| * | |
| * A condition variable is a method of waiting until a certain condition | |
| * becomes true. Conventionally, a condition variable supports three | |
| * operations: (1) sleep; (2) signal, which wakes up one process sleeping | |
| * on the condition variable; and (3) broadcast, which wakes up every | |
| * process sleeping on the condition variable. In our implementation, | |
| * condition variables put a process into an interruptible sleep (so it | |
| * can be canceled prior to the fulfillment of the condition) and do not | |
| * use pointers internally (so that they are safe to use within DSMs). | |
| * | |
| * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group | |
| * Portions Copyright (c) 1994, Regents of the University of California | |
| * | |
| * src/include/storage/condition_variable.h | |
| * | |
| *------------------------------------------------------------------------- | |
| */ | |
| typedef struct | |
| { | |
| slock_t mutex; /* spinlock protecting the wakeup list */ | |
| proclist_head wakeup; /* list of wake-able processes */ | |
| } ConditionVariable; | |
| /* | |
| * Pad a condition variable to a power-of-two size so that an array of | |
| * condition variables does not cross a cache line boundary. | |
| */ | |
| typedef union ConditionVariableMinimallyPadded | |
| { | |
| ConditionVariable cv; | |
| char pad[CV_MINIMAL_SIZE]; | |
| } ConditionVariableMinimallyPadded; | |
| /* Initialize a condition variable. */ | |
| extern void ConditionVariableInit(ConditionVariable *cv); | |
| /* | |
| * To sleep on a condition variable, a process should use a loop which first | |
| * checks the condition, exiting the loop if it is met, and then calls | |
| * ConditionVariableSleep. Spurious wakeups are possible, but should be | |
| * infrequent. After exiting the loop, ConditionVariableCancelSleep must | |
| * be called to ensure that the process is no longer in the wait list for | |
| * the condition variable. | |
| */ | |
| extern void ConditionVariableSleep(ConditionVariable *cv, uint32 wait_event_info); | |
| extern bool ConditionVariableTimedSleep(ConditionVariable *cv, long timeout, | |
| uint32 wait_event_info); | |
| extern bool ConditionVariableCancelSleep(void); | |
| /* | |
| * Optionally, ConditionVariablePrepareToSleep can be called before entering | |
| * the test-and-sleep loop described above. Doing so is more efficient if | |
| * at least one sleep is needed, whereas not doing so is more efficient when | |
| * no sleep is needed because the test condition is true the first time. | |
| */ | |
| extern void ConditionVariablePrepareToSleep(ConditionVariable *cv); | |
| /* Wake up a single waiter (via signal) or all waiters (via broadcast). */ | |
| extern void ConditionVariableSignal(ConditionVariable *cv); | |
| extern void ConditionVariableBroadcast(ConditionVariable *cv); | |