CondVariable

Condition variable definitions.

#include <sync/cv.h>

Structures

CondVariable

Struct representing a condition variable.

Field	Type	Description
seq	_Atomic uint32_t	Wakeup generation. Bumped by every signal and broadcast.
waiters	_Atomic int	The number of threads currently inside CondVarWait().
sem	Semaphore	The semaphore waiting threads block on.

Functions

CondVarInit

Err CondVarInit(CondVariable *cv);

Initialize a condition variable with no waiters.

Parameter	Direction	Description
cv	in	The condition variable to initialize.

Returns: ZUZU_OK on success, negative error code if the underlying semaphore couldn't be created.

CondVarDestroy

Err CondVarDestroy(CondVariable *cv);

Destroy a condition variable.

No thread may be waiting on it.

Parameter	Direction	Description
cv	in	The condition variable to destroy.

Returns: ZUZU_OK on success, ERR_BUSY if the underlying semaphore cannot be destroyed.

CondVarSignal

Err CondVarSignal(CondVariable *cv);

Wake one thread waiting on a condition variable.

Does nothing if no thread is waiting. The caller normally holds the zone that protects the condition, but doesn't have to.

Parameter	Direction	Description
cv	in	The condition variable to signal.

Returns: ZUZU_OK.

CondVarBroadcast

Err CondVarBroadcast(CondVariable *cv);

Wake every thread waiting on a condition variable.

Parameter	Direction	Description
cv	in	The condition variable to signal.

Returns: ZUZU_OK.

CondVarWait

Err CondVarWait(CondVariable *cv, Zone *z);

Release a zone, wait to be signaled, and take the zone again.

The caller must hold z. It is released before blocking and held again when this returns, so the condition must be re-checked in a loop: a wakeup does not guarantee it still holds.

Parameter	Direction	Description
cv	in	The condition variable to wait on.
z	in	The zone that protects the condition; held on entry and on return.

Returns: ZUZU_OK.