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Top Forums Programming pthread_mutex_lock in ANSI C vs using Atomic builtins of GCC Post 302448683 by sehang on Thursday 26th of August 2010 04:20:01 PM
Old 08-26-2010
It is possible create a variable with "volatile" but it is not a primitive type, e.g.

Code:
struct STRUCT {
  volatile int S1;
  volatile char S2;
  volatile  unsigned short int S3;
}
volatile struct STRUCT v1;
volatile enum ENUM v2;
volatile char V3;
volatile unsigned int V4;

v1->S1 = 1;
v1->S2 = 2;
v1->S3 = 3;

v2 = 4;

v3 = 5;

v4 = 6;

Are above operations atomic?
Is any case that "volatile" can not guarantee atomic operation?
 

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ATOMIC_DEC(3)						   BSD Library Functions Manual 					     ATOMIC_DEC(3)

NAME
atomic_dec, atomic_dec_32, atomic_dec_uint, atomic_dec_ulong, atomic_dec_ptr, atomic_dec_64, atomic_dec_32_nv, atomic_dec_uint_nv, atomic_dec_ulong_nv, atomic_dec_ptr_nv, atomic_dec_64_nv -- atomic decrement operations SYNOPSIS
#include <sys/atomic.h> void atomic_dec_32(volatile uint32_t *ptr); void atomic_dec_uint(volatile unsigned int *ptr); void atomic_dec_ulong(volatile unsigned long *ptr); void atomic_dec_ptr(volatile void *ptr); void atomic_dec_64(volatile uint64_t *ptr); uint32_t atomic_dec_32_nv(volatile uint32_t *ptr); unsigned int atomic_dec_uint_nv(volatile unsigned int *ptr); unsigned long atomic_dec_ulong_nv(volatile unsigned long *ptr); void * atomic_dec_ptr_nv(volatile void *ptr); uint64_t atomic_dec_64_nv(volatile uint64_t *ptr); DESCRIPTION
The atomic_dec family of functions decrement (by one) the variable referenced by ptr in an atomic fashion. The *_nv() variants of these functions return the new value. The 64-bit variants of these functions are available only on platforms that can support atomic 64-bit memory access. Applications can check for the availability of 64-bit atomic memory operations by testing if the pre-processor macro __HAVE_ATOMIC64_OPS is defined. SEE ALSO
atomic_ops(3) HISTORY
The atomic_dec functions first appeared in NetBSD 5.0. BSD
April 11, 2007 BSD
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