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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2021 Vladimir Kondratyev <wulf@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef _LINUXKPI_LINUX_SEQLOCK_H__
#define _LINUXKPI_LINUX_SEQLOCK_H__
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/rwlock.h>
#include <sys/seqc.h>
#include <linux/mutex.h>
struct lock_class_key;
struct seqcount {
seqc_t seqc;
};
typedef struct seqcount seqcount_t;
struct seqlock {
struct mtx seql_lock;
struct seqcount seql_count;
};
typedef struct seqlock seqlock_t;
struct seqcount_mutex {
struct mutex *seqm_lock;
struct seqcount seqm_count;
};
typedef struct seqcount_mutex seqcount_mutex_t;
static inline void
__seqcount_init(struct seqcount *seqcount, const char *name __unused,
struct lock_class_key *key __unused)
{
seqcount->seqc = 0;
}
#define seqcount_init(seqcount) __seqcount_init(seqcount, NULL, NULL)
static inline void
seqcount_mutex_init(struct seqcount_mutex *seqcount, struct mutex *mutex)
{
seqcount->seqm_lock = mutex;
seqcount_init(&seqcount->seqm_count);
}
#define write_seqcount_begin(s) \
_Generic(*(s), \
struct seqcount: lkpi_write_seqcount_begin, \
struct seqcount_mutex: lkpi_write_seqcount_mutex_begin \
)(s)
static inline void
lkpi_write_seqcount_begin(struct seqcount *seqcount)
{
seqc_sleepable_write_begin(&seqcount->seqc);
}
static inline void
lkpi_write_seqcount_mutex_begin(struct seqcount_mutex *seqcount)
{
mutex_lock(seqcount->seqm_lock);
lkpi_write_seqcount_begin(&seqcount->seqm_count);
}
#define write_seqcount_end(s) \
_Generic(*(s), \
struct seqcount: lkpi_write_seqcount_end, \
struct seqcount_mutex: lkpi_write_seqcount_mutex_end \
)(s)
static inline void
lkpi_write_seqcount_end(struct seqcount *seqcount)
{
seqc_sleepable_write_end(&seqcount->seqc);
}
static inline void
lkpi_write_seqcount_mutex_end(struct seqcount_mutex *seqcount)
{
lkpi_write_seqcount_end(&seqcount->seqm_count);
mutex_unlock(seqcount->seqm_lock);
}
#define read_seqcount_begin(s) \
_Generic(*(s), \
struct seqcount: lkpi_read_seqcount_begin, \
struct seqcount_mutex: lkpi_read_seqcount_mutex_begin \
)(s)
static inline unsigned
lkpi_read_seqcount_begin(const struct seqcount *seqcount)
{
return (seqc_read(&seqcount->seqc));
}
static inline unsigned
lkpi_read_seqcount_mutex_begin(const struct seqcount_mutex *seqcount)
{
return (lkpi_read_seqcount_begin(&seqcount->seqm_count));
}
static inline unsigned
raw_read_seqcount(const struct seqcount *seqcount)
{
return (seqc_read_any(&seqcount->seqc));
}
/*
* XXX: Are predicts from inline functions still not honored by clang?
*/
#define __read_seqcount_retry(seqcount, gen) \
(!seqc_consistent_no_fence(&(seqcount)->seqc, gen))
#define read_seqcount_retry(s, old) \
_Generic(*(s), \
struct seqcount: lkpi_read_seqcount_retry, \
struct seqcount_mutex: lkpi_read_seqcount_mutex_retry \
)(s, old)
static inline int
lkpi_read_seqcount_retry(
const struct seqcount *seqcount, unsigned int old)
{
return (!seqc_consistent(&seqcount->seqc, old));
}
static inline int
lkpi_read_seqcount_mutex_retry(
const struct seqcount_mutex *seqcount, unsigned int old)
{
return (!seqc_consistent(&seqcount->seqm_count.seqc, old));
}
static inline void
seqlock_init(struct seqlock *seqlock)
{
/*
* Don't enroll to witness(4) to avoid orphaned references after struct
* seqlock has been freed. There is no seqlock destructor exists so we
* can't expect automatic mtx_destroy() execution before free().
*/
mtx_init(&seqlock->seql_lock, "seqlock", NULL, MTX_DEF|MTX_NOWITNESS);
seqcount_init(&seqlock->seql_count);
}
static inline void
lkpi_write_seqlock(struct seqlock *seqlock, const bool irqsave)
{
mtx_lock(&seqlock->seql_lock);
if (irqsave)
critical_enter();
write_seqcount_begin(&seqlock->seql_count);
}
static inline void
write_seqlock(struct seqlock *seqlock)
{
lkpi_write_seqlock(seqlock, false);
}
static inline void
lkpi_write_sequnlock(struct seqlock *seqlock, const bool irqsave)
{
write_seqcount_end(&seqlock->seql_count);
if (irqsave)
critical_exit();
mtx_unlock(&seqlock->seql_lock);
}
static inline void
write_sequnlock(struct seqlock *seqlock)
{
lkpi_write_sequnlock(seqlock, false);
}
/*
* Disable preemption when the consumer wants to disable interrupts. This
* ensures that the caller won't be starved if it is preempted by a
* higher-priority reader, but assumes that the caller won't perform any
* blocking operations while holding the write lock; probably a safe
* assumption.
*/
#define write_seqlock_irqsave(seqlock, flags) do { \
(flags) = 0; \
lkpi_write_seqlock(seqlock, true); \
} while (0)
static inline void
write_sequnlock_irqrestore(struct seqlock *seqlock,
unsigned long flags __unused)
{
lkpi_write_sequnlock(seqlock, true);
}
static inline unsigned
read_seqbegin(const struct seqlock *seqlock)
{
return (read_seqcount_begin(&seqlock->seql_count));
}
#define read_seqretry(seqlock, gen) \
read_seqcount_retry(&(seqlock)->seql_count, gen)
#endif /* _LINUXKPI_LINUX_SEQLOCK_H__ */
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