30d4f9e888
They provide relaxed-ordered atomic access semantic. Due to the FreeBSD memory model, the operations are syntaxical wrappers around the volatile accesses. The volatile qualifier is used to ensure that the access not optimized out and in turn depends on the volatile semantic as implemented by supported compilers. The motivation for adding the operation is to help people coming from other systems or knowing the C11/C++ standards where atomics have special type and require use of the special access operations. It is still the case that FreeBSD requires plain load and stores of aligned integer types to be atomic. Suggested by: jhb Reviewed by: alc, jhb Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D13534
376 lines
10 KiB
C
376 lines
10 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 1998 Doug Rabson.
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* Copyright (c) 2001 Jake Burkholder.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: FreeBSD: src/sys/i386/include/atomic.h,v 1.20 2001/02/11
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* $FreeBSD$
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*/
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#ifndef _MACHINE_ATOMIC_H_
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#define _MACHINE_ATOMIC_H_
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#include <machine/cpufunc.h>
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#define mb() __asm__ __volatile__ ("membar #MemIssue": : :"memory")
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#define wmb() mb()
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#define rmb() mb()
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#include <sys/atomic_common.h>
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/* Userland needs different ASI's. */
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#ifdef _KERNEL
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#define __ASI_ATOMIC ASI_N
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#else
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#define __ASI_ATOMIC ASI_P
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#endif
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/*
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* Various simple arithmetic on memory which is atomic in the presence
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* of interrupts and multiple processors. See atomic(9) for details.
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* Note that efficient hardware support exists only for the 32 and 64
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* bit variants; the 8 and 16 bit versions are not provided and should
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* not be used in MI code.
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*
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* This implementation takes advantage of the fact that the sparc64
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* cas instruction is both a load and a store. The loop is often coded
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* as follows:
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*
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* do {
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* expect = *p;
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* new = expect + 1;
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* } while (cas(p, expect, new) != expect);
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*
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* which performs an unnnecessary load on each iteration that the cas
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* operation fails. Modified as follows:
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*
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* expect = *p;
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* for (;;) {
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* new = expect + 1;
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* result = cas(p, expect, new);
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* if (result == expect)
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* break;
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* expect = result;
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* }
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*
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* the return value of cas is used to avoid the extra reload.
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*
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* We only include a memory barrier in the rel variants as in total store
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* order which we use for running the kernel and all of the userland atomic
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* loads and stores behave as if the were followed by a membar with a mask
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* of #LoadLoad | #LoadStore | #StoreStore. In order to be also sufficient
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* for use of relaxed memory ordering, the atomic_cas() in the acq variants
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* additionally would have to be followed by a membar #LoadLoad | #LoadStore.
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* Due to the suggested assembly syntax of the membar operands containing a
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* # character, they cannot be used in macros. The cmask and mmask bits thus
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* are hard coded in machine/cpufunc.h and used here through macros.
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* Hopefully the bit numbers won't change in the future.
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*/
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#define itype(sz) uint ## sz ## _t
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#define atomic_cas_32(p, e, s) casa((p), (e), (s), __ASI_ATOMIC)
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#define atomic_cas_64(p, e, s) casxa((p), (e), (s), __ASI_ATOMIC)
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#define atomic_cas(p, e, s, sz) \
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atomic_cas_ ## sz((p), (e), (s))
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#define atomic_cas_acq(p, e, s, sz) ({ \
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itype(sz) v; \
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v = atomic_cas((p), (e), (s), sz); \
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__compiler_membar(); \
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v; \
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})
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#define atomic_cas_rel(p, e, s, sz) ({ \
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itype(sz) v; \
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membar(LoadStore | StoreStore); \
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v = atomic_cas((p), (e), (s), sz); \
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v; \
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})
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#define atomic_op(p, op, v, sz) ({ \
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itype(sz) e, r, s; \
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for (e = *(volatile itype(sz) *)(p);; e = r) { \
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s = e op (v); \
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r = atomic_cas_ ## sz((p), e, s); \
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if (r == e) \
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break; \
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} \
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e; \
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})
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#define atomic_op_acq(p, op, v, sz) ({ \
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itype(sz) t; \
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t = atomic_op((p), op, (v), sz); \
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__compiler_membar(); \
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t; \
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})
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#define atomic_op_rel(p, op, v, sz) ({ \
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itype(sz) t; \
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membar(LoadStore | StoreStore); \
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t = atomic_op((p), op, (v), sz); \
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t; \
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})
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#define atomic_ld_acq(p, sz) ({ \
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itype(sz) v; \
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v = atomic_cas((p), 0, 0, sz); \
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__compiler_membar(); \
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v; \
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})
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#define atomic_ld_clear(p, sz) ({ \
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itype(sz) e, r; \
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for (e = *(volatile itype(sz) *)(p);; e = r) { \
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r = atomic_cas((p), e, 0, sz); \
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if (r == e) \
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break; \
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} \
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e; \
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})
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#define atomic_st(p, v, sz) do { \
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itype(sz) e, r; \
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for (e = *(volatile itype(sz) *)(p);; e = r) { \
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r = atomic_cas((p), e, (v), sz); \
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if (r == e) \
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break; \
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} \
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} while (0)
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#define atomic_st_acq(p, v, sz) do { \
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atomic_st((p), (v), sz); \
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__compiler_membar(); \
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} while (0)
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#define atomic_st_rel(p, v, sz) do { \
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membar(LoadStore | StoreStore); \
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atomic_st((p), (v), sz); \
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} while (0)
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#define ATOMIC_GEN(name, ptype, vtype, atype, sz) \
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\
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static __inline vtype \
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atomic_add_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op((p), +, (v), sz)); \
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} \
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static __inline vtype \
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atomic_add_acq_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_acq((p), +, (v), sz)); \
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} \
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static __inline vtype \
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atomic_add_rel_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_rel((p), +, (v), sz)); \
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} \
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\
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static __inline vtype \
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atomic_clear_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op((p), &, ~(v), sz)); \
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} \
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static __inline vtype \
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atomic_clear_acq_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_acq((p), &, ~(v), sz)); \
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} \
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static __inline vtype \
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atomic_clear_rel_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_rel((p), &, ~(v), sz)); \
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} \
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\
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static __inline int \
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atomic_cmpset_ ## name(volatile ptype p, vtype e, vtype s) \
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{ \
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return (((vtype)atomic_cas((p), (e), (s), sz)) == (e)); \
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} \
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static __inline int \
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atomic_cmpset_acq_ ## name(volatile ptype p, vtype e, vtype s) \
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{ \
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return (((vtype)atomic_cas_acq((p), (e), (s), sz)) == (e)); \
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} \
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static __inline int \
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atomic_cmpset_rel_ ## name(volatile ptype p, vtype e, vtype s) \
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{ \
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return (((vtype)atomic_cas_rel((p), (e), (s), sz)) == (e)); \
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} \
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\
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static __inline int \
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atomic_fcmpset_ ## name(volatile ptype p, vtype *ep, vtype s) \
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{ \
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vtype t; \
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\
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t = (vtype)atomic_cas((p), (*ep), (s), sz); \
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if (t == (*ep)) \
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return (1); \
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*ep = t; \
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return (0); \
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} \
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static __inline int \
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atomic_fcmpset_acq_ ## name(volatile ptype p, vtype *ep, vtype s) \
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{ \
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vtype t; \
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\
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t = (vtype)atomic_cas_acq((p), (*ep), (s), sz); \
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if (t == (*ep)) \
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return (1); \
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*ep = t; \
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return (0); \
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} \
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static __inline int \
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atomic_fcmpset_rel_ ## name(volatile ptype p, vtype *ep, vtype s) \
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{ \
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vtype t; \
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\
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t = (vtype)atomic_cas_rel((p), (*ep), (s), sz); \
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if (t == (*ep)) \
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return (1); \
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*ep = t; \
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return (0); \
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} \
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\
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static __inline vtype \
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atomic_load_ ## name(volatile ptype p) \
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{ \
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return ((vtype)atomic_cas((p), 0, 0, sz)); \
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} \
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static __inline vtype \
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atomic_load_acq_ ## name(volatile ptype p) \
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{ \
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return ((vtype)atomic_cas_acq((p), 0, 0, sz)); \
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} \
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\
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static __inline vtype \
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atomic_readandclear_ ## name(volatile ptype p) \
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{ \
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return ((vtype)atomic_ld_clear((p), sz)); \
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} \
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\
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static __inline vtype \
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atomic_set_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op((p), |, (v), sz)); \
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} \
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static __inline vtype \
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atomic_set_acq_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_acq((p), |, (v), sz)); \
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} \
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static __inline vtype \
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atomic_set_rel_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_rel((p), |, (v), sz)); \
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} \
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\
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static __inline vtype \
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atomic_subtract_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op((p), -, (v), sz)); \
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} \
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static __inline vtype \
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atomic_subtract_acq_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_acq((p), -, (v), sz)); \
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} \
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static __inline vtype \
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atomic_subtract_rel_ ## name(volatile ptype p, atype v) \
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{ \
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return ((vtype)atomic_op_rel((p), -, (v), sz)); \
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} \
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\
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static __inline void \
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atomic_store_acq_ ## name(volatile ptype p, vtype v) \
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{ \
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atomic_st_acq((p), (v), sz); \
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} \
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static __inline void \
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atomic_store_rel_ ## name(volatile ptype p, vtype v) \
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{ \
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atomic_st_rel((p), (v), sz); \
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}
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static __inline void
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atomic_thread_fence_acq(void)
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{
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__compiler_membar();
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}
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static __inline void
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atomic_thread_fence_rel(void)
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{
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__compiler_membar();
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}
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static __inline void
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atomic_thread_fence_acq_rel(void)
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{
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__compiler_membar();
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}
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static __inline void
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atomic_thread_fence_seq_cst(void)
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{
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membar(LoadLoad | LoadStore | StoreStore | StoreLoad);
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}
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ATOMIC_GEN(int, u_int *, u_int, u_int, 32);
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ATOMIC_GEN(32, uint32_t *, uint32_t, uint32_t, 32);
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ATOMIC_GEN(long, u_long *, u_long, u_long, 64);
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ATOMIC_GEN(64, uint64_t *, uint64_t, uint64_t, 64);
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ATOMIC_GEN(ptr, uintptr_t *, uintptr_t, uintptr_t, 64);
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#define atomic_fetchadd_int atomic_add_int
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#define atomic_fetchadd_32 atomic_add_32
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#define atomic_fetchadd_long atomic_add_long
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#define atomic_fetchadd_64 atomic_add_64
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#undef ATOMIC_GEN
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#undef atomic_cas
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#undef atomic_cas_acq
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#undef atomic_cas_rel
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#undef atomic_op
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#undef atomic_op_acq
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#undef atomic_op_rel
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#undef atomic_ld_acq
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#undef atomic_ld_clear
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#undef atomic_st
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#undef atomic_st_acq
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#undef atomic_st_rel
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#endif /* !_MACHINE_ATOMIC_H_ */
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