atomic_add

Section: Kernel Functions (9)
Updated: $Date:$
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NAME

atomic_add, atomic_sub, atomic_inc, atomic_dec - thread/SMP safe arithmetic on atomic data  

SYNOPSIS

#include <asm/atomic.h>

void atomic_add(int i, volatile atomic_t*v)
void atomic_sub(int i, volatile atomic_t*v)
void atomic_inc(volatile atomic_t*v)
void atomic_dec(volatile atomic_t*v)
int atomic_read(volatile atomic_t*v)
void atomic_set(volatile atomic_t*v, int i)
int atomic_dec_and_test(volatile atomic_t*v)

 

DESCRIPTION

These functions manipulate variables of type atomic_t is SMP and interrupt safe ways. These variables can be used to hold spin locks or SMP-safe reference counters. These functions guarantee that the operation that they represent is performed correctly. If necessary, hardware bus locking is performed to protect the operation. Usually, the CPU has some sort of atomic instructions that allow these operations to be performed quickly and safely.

The atomic_dec_and_test decrements the atomic variable, and returns true if the result is zero. This function is particularly useful in implementing spin locks on SMP systems.  

RETURN VALUE

The atomic_read function returns the integer value of the atomic variable.

The atomic_dec_and_test returns TRUE if the value becomes zero after the decrement.  

AVAILABILITY

Linux 2.0+  

SEE ALSO

intro(9)  

AUTHOR

Stephen Williams <steve@icarus.com>  

BUGS

The read and set operations generally have no special protections.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
AVAILABILITY
SEE ALSO
AUTHOR
BUGS
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