Atomic locks

Atomic locks are synchronization primitives that are used to ensure that basic arithmetic and bit operations are executed without preemption.

DDI atomic locks

The following atomic lock functions and structures are supported in DDI version 6 and later versions:

ATOMIC_INT(D4)

definition of atomic_int structure

ATOMIC_INT_ALLOC(D3)

allocate an atomic_int object

ATOMIC_INT_INIT(D3)

initialize an atomic_int object

ATOMIC_INT_ADD(D3)

add to an atomic_int value

ATOMIC_INT_SUB(D3)

subtract from an atomic_int value

ATOMIC_INT_INCR(D3)

increment an atomic_int structure

ATOMIC_INT_DECR(D3)

decrement an atomic_int value

ATOMIC_INT_READ(D3)

read value stored within an atomic_int object

ATOMIC_INT_WRITE(D3)

write value into an atomic_int object

ATOMIC_INT_DEALLOC(D3)

free an atomic_int object

The atomicity properties of ATOMIC_INT objects are strictly limited to a single object. Drivers should be careful not to assume any ordering of operations between two instances of ATOMIC_INT objects, or between these objects and objects whose access patterns are serialized by means of locks, unless such ordering is explicitly arranged for in the driver through use of locks. In particular, drivers should not assume that arbitrary writes will be observed in any particular order by another engine.

For any single ATOMIC_INT object, the following operations on that object are serialized: ATOMIC_INT_ADD(D3), ATOMIC_INT_DECR(D3), ATOMIC_INT_INCR(D3), ATOMIC_INT_READ(D3), ATOMIC_INT_SUB(D3), and ATOMIC_INT_WRITE(D3). This means that the results of a set of these operations on multiple engines will appear as though they had occurred in some specific order on a single engine.

ODDI atomic locks

SCO OpenServer 5 atomic locking functions are documented on the atomic(D3oddi) manual page. The SCO OpenServer 5 atomic locks are a set of functions whose names determine the operation and size of the arguments. The following tables show the full set of SCO OpenServer 5 quick lock functions:

Quick locks with two parameters -- qaddl(void,long)

Operation	long	ulong	int	uint	short	ushort	char	uchar
addition	qaddl	qaddul	qaddi	qaddui	qaddw	qadduw	qaddb	qaddub
subtraction	qsubl	qsubul	qsubi	qsubui	qsubw	qsubuw	qsubb	qsubub
and	qandl	qandul	qandi	qandui	qandw	qanduw	qandb	qandub
exchange	qxchgl	qxchgul	qxchgi	qxchgui	qxchgw	qxchguw	qxchgb	qxchgub
or	qorl	qorul	qori	qorui	qorw	qoruw	qorb	qorub

Quick locks with one parameter --qincl(void)

Operation	long	ulong	int	uint	short	ushort	char	uchar
increment	qincl	qincul	qinci	qincui	qincw	qincuw	qincb	qincub
decrement	qdecl	qdecul	qdeci	qdecui	qdecw	qdecuw	qdecb	qdecub
zero	qzerol	qzeroul	qzeroi	qzeroui	qzerow	qzerouw	qzerob	qzeroub

Bit test/set locks

Operation	long	ulong	int	uint	short	ushort	char	uchar
bit test/set	qbtsl	qbtsul	qbtsi	qbtsui	--	--	--	--