atomics.c File Reference

#include "postgres.h"
#include "miscadmin.h"
#include "port/atomics.h"
#include "storage/spin.h"

Include dependency graph for atomics.c:

Go to the source code of this file.

Functions
void	pg_atomic_init_u64_impl (volatile pg_atomic_uint64 *ptr, uint64 val_)
bool	pg_atomic_compare_exchange_u64_impl (volatile pg_atomic_uint64 *ptr, uint64 *expected, uint64 newval)
uint64	pg_atomic_fetch_add_u64_impl (volatile pg_atomic_uint64 *ptr, int64 add_)

Function Documentation

pg_atomic_compare_exchange_u64_impl()

bool pg_atomic_compare_exchange_u64_impl	(	volatile pg_atomic_uint64 *	ptr,
		uint64 *	expected,
		uint64	newval
	)

Definition at line 34 of file atomics.c.

{
    bool        ret;
 
    /*
     * Do atomic op under a spinlock. It might look like we could just skip
     * the cmpxchg if the lock isn't available, but that'd just emulate a
     * 'weak' compare and swap. I.e. one that allows spurious failures. Since
     * several algorithms rely on a strong variant and that is efficiently
     * implementable on most major architectures let's emulate it here as
     * well.
     */
    SpinLockAcquire((slock_t *) &ptr->sema);
 
    /* perform compare/exchange logic */
    ret = ptr->value == *expected;
    *expected = ptr->value;
    if (ret)
        ptr->value = newval;
 
    /* and release lock */
    SpinLockRelease((slock_t *) &ptr->sema);
 
    return ret;
}

References newval, pg_atomic_uint64::sema, SpinLockAcquire, SpinLockRelease, and pg_atomic_uint64::value.

Referenced by pg_atomic_compare_exchange_u64(), and pg_atomic_read_u64_impl().

pg_atomic_fetch_add_u64_impl()

uint64 pg_atomic_fetch_add_u64_impl	(	volatile pg_atomic_uint64 *	ptr,
		int64	add_
	)

Definition at line 62 of file atomics.c.

{
    uint64      oldval;
 
    SpinLockAcquire((slock_t *) &ptr->sema);
    oldval = ptr->value;
    ptr->value += add_;
    SpinLockRelease((slock_t *) &ptr->sema);
    return oldval;
}

References pg_atomic_uint64::sema, SpinLockAcquire, SpinLockRelease, and pg_atomic_uint64::value.

Referenced by pg_atomic_fetch_add_u64().

pg_atomic_init_u64_impl()

void pg_atomic_init_u64_impl	(	volatile pg_atomic_uint64 *	ptr,
		uint64	val_
	)

Definition at line 24 of file atomics.c.

{
    StaticAssertDecl(sizeof(ptr->sema) >= sizeof(slock_t),
                     "size mismatch of atomic_uint64 vs slock_t");
 
    SpinLockInit((slock_t *) &ptr->sema);
    ptr->value = val_;
}

References pg_atomic_uint64::sema, SpinLockInit, StaticAssertDecl, and pg_atomic_uint64::value.

Referenced by pg_atomic_init_u64().