bge_atomic.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include "sys/bge_impl.h"
/*
* Atomically decrement a counter, but only if it will remain
* strictly positive (greater than zero) afterwards. We return
* the decremented value if so, otherwise zero (in which case
* the counter is unchanged).
*
* This is used for keeping track of available resources such
* as transmit ring slots ...
*/
uint64_t
bge_atomic_reserve(uint64_t *count_p, uint64_t n)
{
uint64_t oldval;
uint64_t newval;
/* ATOMICALLY */
do {
oldval = *count_p;
newval = oldval - n;
if (oldval <= n)
return (0); /* no resources left */
} while (cas64(count_p, oldval, newval) != oldval);
return (newval);
}
/*
* Atomically increment a counter
*/
void
bge_atomic_renounce(uint64_t *count_p, uint64_t n)
{
uint64_t oldval;
uint64_t newval;
/* ATOMICALLY */
do {
oldval = *count_p;
newval = oldval + n;
} while (cas64(count_p, oldval, newval) != oldval);
}
/*
* Atomically claim a slot in a descriptor ring
*/
uint64_t
bge_atomic_claim(uint64_t *count_p, uint64_t limit)
{
uint64_t oldval;
uint64_t newval;
/* ATOMICALLY */
do {
oldval = *count_p;
newval = NEXT(oldval, limit);
} while (cas64(count_p, oldval, newval) != oldval);
return (oldval);
}
/*
* Atomically clear bits in a 64-bit word, returning
* the value it had *before* the bits were cleared.
*/
uint64_t
bge_atomic_clr64(uint64_t *sp, uint64_t bits)
{
uint64_t oldval;
uint64_t newval;
/* ATOMICALLY */
do {
oldval = *sp;
newval = oldval & ~bits;
} while (cas64(sp, oldval, newval) != oldval);
return (oldval);
}
/*
* Atomically shift a 32-bit word left, returning
* the value it had *before* the shift was applied
*/
uint32_t
bge_atomic_shl32(uint32_t *sp, uint_t count)
{
uint32_t oldval;
uint32_t newval;
/* ATOMICALLY */
do {
oldval = *sp;
newval = oldval << count;
} while (cas32(sp, oldval, newval) != oldval);
return (oldval);
}