#include "postgres.h"

#include "fmgr.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"


PG_MODULE_MAGIC;

static pg_atomic_uint32 *globptr = NULL;

int32 globjunk = 0;

PG_FUNCTION_INFO_V1(my_test_atomic_ops);

Datum
my_test_atomic_ops(PG_FUNCTION_ARGS)
{
	int64		count = PG_GETARG_INT64(0);
	int32 result;
	pg_atomic_uint32 *myptr;
	int32 junk = 0;

	if (globptr == NULL)
	{
		/* First time through in this process; find shared memory */
		bool		found;

		LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);

		globptr = ShmemInitStruct("my_test_atomic_ops",
								sizeof(*globptr),
								&found);

		if (!found)
		{
			/* First time through anywhere */
			pg_atomic_init_u32(globptr, 0);
		}

		LWLockRelease(AddinShmemInitLock);
	}

	myptr = globptr;

	while (count-- > 0)
	{
		junk += pg_atomic_fetch_add_u32(myptr, 1);
	}

	globjunk += junk;

	result = pg_atomic_read_u32(myptr);

	PG_RETURN_INT32(result);
}