ATOMIC_INT(D4)

ATOMIC_INT -- atomic integer

Syntax

   #include <sys/types.h>
   #include <sys/ksynch.h>
   #include <sys/ddi.h>
   
   typedef atomic_int_t;

Description

The ATOMIC_INT structure stores an integer value that can be atomically accessed from multiple engines. Within a processor family, the precision of the value stored in the ATOMIC_INT is at least as great as the data type int.

Usage

An ATOMIC_INT structure, an atomic_int_t, can be used by a driver to keep a consistent counter value across multiple engines without the need to acquire locks. Specifically, 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.

The ATOMIC_INT objects must be allocated by the ATOMIC_INT_ALLOC(D3) function and initialized by the ATOMIC_INT_INIT(D3) function before they are used. They may be freed with the ATOMIC_INT_DEALLOC(D3) function.

Warnings

The atomicity properties of ATOMIC_INT objects (as defined in the section above) 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 set up 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.

Structure definition

The ATOMIC_INT structure contains no driver accessible fields.

Applicable hardware

All

Version applicability

ddi: 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp

Difference between versions

References

ATOMIC_INT_ADD(D3), ATOMIC_INT_ALLOC(D3), ATOMIC_INT_DEALLOC(D3), ATOMIC_INT_DECR(D3), ATOMIC_INT_INCR(D3), ATOMIC_INT_INIT(D3), ATOMIC_INT_READ(D3), ATOMIC_INT_SUB(D3), ATOMIC_INT_WRITE(D3)