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/*
* Berkeley Lab Checkpoint/Restart (BLCR) for Linux is Copyright (c)
* 2003, The Regents of the University of California, through Lawrence
* Berkeley National Laboratory (subject to receipt of any required
* approvals from the U.S. Dept. of Energy). All rights reserved.
*
* Portions may be copyrighted by others, as may be noted in specific
* copyright notices within specific files.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* $Id: cr_atomic.h,v 1.10 2007/02/16 20:23:24 phargrov Exp $
*/
#ifndef _CR_ATOMIC_H
#define _CR_ATOMIC_H 1
// Define cri_atomic_t and five required operations:
// read, write, inc, dec-and-test, compare-and-swap
typedef volatile unsigned int cri_atomic_t;
// Single-word reads are naturally atomic on Pentium-family
CR_INLINE unsigned int
cri_atomic_read(cri_atomic_t *p)
{
__asm__ __volatile__("": : :"memory");
return *p;
}
// Single-word writes are naturally atomic on Pentium-family
CR_INLINE void
cri_atomic_write(cri_atomic_t *p, unsigned int val)
{
*p = val;
__asm__ __volatile__("": : :"memory");
}
// Increment requires lock prefix for SMPs
CR_INLINE void
cri_atomic_inc(cri_atomic_t *p)
{
__asm__ __volatile__ ("lock; incl %0"
: "=m" (*p)
: "m" (*p)
: "cc", "memory");
}
// Dec-and-test requires lock prefix for SMPs
// Returns non-zero if value reaches zero
CR_INLINE int
cri_atomic_dec_and_test(cri_atomic_t *p)
{
register unsigned char ret;
__asm__ __volatile__ ("lock; decl %0; sete %1"
: "=m" (*p), "=qm" (ret)
: "m" (*p)
: "cc", "memory");
return ret;
}
// cri_cmp_swap()
//
// Atomic compare and exchange (swap).
// Atomic equivalent of:
// if (*p == oldval) {
// *p = newval;
// return NONZERO;
// } else {
// return 0;
// }
//
// Based on glibc source (LGPL)
// XXX: this will fail on an old i386
CR_INLINE unsigned int
cri_cmp_swap(cri_atomic_t *p, unsigned int oldval, unsigned int newval)
{
register unsigned char ret;
register unsigned int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval)
: "cc", "memory");
return ret;
}
#endif
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