mirror of https://github.com/F-Stack/f-stack.git
144 lines
3.3 KiB
C
144 lines
3.3 KiB
C
/*-
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* Copyright (c) 2014 Mateusz Guzik <mjg@FreeBSD.org>
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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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* $FreeBSD$
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*/
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#ifndef _SYS_SEQC_H_
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#define _SYS_SEQC_H_
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#ifdef _KERNEL
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#include <sys/systm.h>
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#endif
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#include <sys/types.h>
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/*
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* seqc_t may be included in structs visible to userspace
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*/
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#include <sys/_seqc.h>
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#ifdef _KERNEL
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/* A hack to get MPASS macro */
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#include <sys/lock.h>
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#include <machine/cpu.h>
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/*
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* Predicts from inline functions are not honored by clang.
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*/
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#define seqc_in_modify(seqc) ({ \
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seqc_t __seqc = (seqc); \
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\
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__predict_false(__seqc & 1); \
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})
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static __inline void
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seqc_write_begin(seqc_t *seqcp)
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{
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critical_enter();
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MPASS(!seqc_in_modify(*seqcp));
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*seqcp += 1;
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atomic_thread_fence_rel();
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}
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static __inline void
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seqc_write_end(seqc_t *seqcp)
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{
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atomic_thread_fence_rel();
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*seqcp += 1;
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MPASS(!seqc_in_modify(*seqcp));
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critical_exit();
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}
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static __inline seqc_t
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seqc_read_any(const seqc_t *seqcp)
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{
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return (atomic_load_acq_int(__DECONST(seqc_t *, seqcp)));
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}
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static __inline seqc_t
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seqc_read_notmodify(const seqc_t *seqcp)
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{
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return (atomic_load_acq_int(__DECONST(seqc_t *, seqcp)) & ~1);
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}
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static __inline seqc_t
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seqc_read(const seqc_t *seqcp)
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{
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seqc_t ret;
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for (;;) {
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ret = seqc_read_any(seqcp);
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if (seqc_in_modify(ret)) {
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cpu_spinwait();
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continue;
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}
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break;
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}
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return (ret);
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}
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#define seqc_consistent_nomb(seqcp, oldseqc) ({ \
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const seqc_t *__seqcp = (seqcp); \
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seqc_t __oldseqc = (oldseqc); \
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\
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MPASS(!(seqc_in_modify(__oldseqc))); \
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__predict_true(*__seqcp == __oldseqc); \
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})
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#define seqc_consistent(seqcp, oldseqc) ({ \
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atomic_thread_fence_acq(); \
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seqc_consistent_nomb(seqcp, oldseqc); \
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})
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/*
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* Variant which does not critical enter/exit.
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*/
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static __inline void
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seqc_sleepable_write_begin(seqc_t *seqcp)
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{
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MPASS(!seqc_in_modify(*seqcp));
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*seqcp += 1;
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atomic_thread_fence_rel();
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}
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static __inline void
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seqc_sleepable_write_end(seqc_t *seqcp)
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{
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atomic_thread_fence_rel();
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*seqcp += 1;
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MPASS(!seqc_in_modify(*seqcp));
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}
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#endif /* _KERNEL */
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#endif /* _SYS_SEQC_H_ */
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