61 lines
2.5 KiB
C
61 lines
2.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* condition_variable.h
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* Condition variables
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*
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* A condition variable is a method of waiting until a certain condition
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* becomes true. Conventionally, a condition variable supports three
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* operations: (1) sleep; (2) signal, which wakes up one process sleeping
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* on the condition variable; and (3) broadcast, which wakes up every
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* process sleeping on the condition variable. In our implementation,
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* condition variables put a process into an interruptible sleep (so it
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* can be cancelled prior to the fulfillment of the condition) and do not
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* use pointers internally (so that they are safe to use within DSMs).
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/condition_variable.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef CONDITION_VARIABLE_H
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#define CONDITION_VARIABLE_H
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#include "storage/s_lock.h"
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#include "storage/proclist_types.h"
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typedef struct
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{
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slock_t mutex; /* spinlock protecting the wakeup list */
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proclist_head wakeup; /* list of wake-able processes */
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} ConditionVariable;
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/* Initialize a condition variable. */
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extern void ConditionVariableInit(ConditionVariable *cv);
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/*
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* To sleep on a condition variable, a process should use a loop which first
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* checks the condition, exiting the loop if it is met, and then calls
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* ConditionVariableSleep. Spurious wakeups are possible, but should be
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* infrequent. After exiting the loop, ConditionVariableCancelSleep must
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* be called to ensure that the process is no longer in the wait list for
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* the condition variable.
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*/
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extern void ConditionVariableSleep(ConditionVariable *cv, uint32 wait_event_info);
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extern void ConditionVariableCancelSleep(void);
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/*
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* Optionally, ConditionVariablePrepareToSleep can be called before entering
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* the test-and-sleep loop described above. Doing so is more efficient if
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* at least one sleep is needed, whereas not doing so is more efficient when
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* no sleep is needed because the test condition is true the first time.
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*/
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extern void ConditionVariablePrepareToSleep(ConditionVariable *cv);
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/* Wake up a single waiter (via signal) or all waiters (via broadcast). */
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extern void ConditionVariableSignal(ConditionVariable *cv);
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extern void ConditionVariableBroadcast(ConditionVariable *cv);
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#endif /* CONDITION_VARIABLE_H */
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