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#ifndef __LINUX_SEQLOCK_H
#define __LINUX_SEQLOCK_H
#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <asm/processor.h>
typedef struct {
unsigned sequence;
spinlock_t lock;
} seqlock_t;
#define __SEQLOCK_UNLOCKED(lockname) \
{ 0, __SPIN_LOCK_UNLOCKED(lockname) }
#define seqlock_init(x) \
do { \
(x)->sequence = 0; \
spin_lock_init(&(x)->lock); \
} while (0)
#define DEFINE_SEQLOCK(x) \
seqlock_t x = __SEQLOCK_UNLOCKED(x)
static inline void write_seqlock(seqlock_t *sl)
{
spin_lock(&sl->lock);
++sl->sequence;
smp_wmb();
}
static inline void write_sequnlock(seqlock_t *sl)
{
smp_wmb();
sl->sequence++;
spin_unlock(&sl->lock);
}
static inline int write_tryseqlock(seqlock_t *sl)
{
int ret = spin_trylock(&sl->lock);
if (ret) {
++sl->sequence;
smp_wmb();
}
return ret;
}
static __always_inline unsigned read_seqbegin(const seqlock_t *sl)
{
unsigned ret;
repeat:
ret = ACCESS_ONCE(sl->sequence);
if (unlikely(ret & 1)) {
cpu_relax();
goto repeat;
}
smp_rmb();
return ret;
}
static __always_inline int read_seqretry(const seqlock_t *sl, unsigned start)
{
smp_rmb();
return unlikely(sl->sequence != start);
}
typedef struct seqcount {
unsigned sequence;
} seqcount_t;
#define SEQCNT_ZERO { 0 }
#define seqcount_init(x) do { *(x) = (seqcount_t) SEQCNT_ZERO; } while (0)
static inline unsigned __read_seqcount_begin(const seqcount_t *s)
{
unsigned ret;
repeat:
ret = ACCESS_ONCE(s->sequence);
if (unlikely(ret & 1)) {
cpu_relax();
goto repeat;
}
return ret;
}
static inline unsigned read_seqcount_begin(const seqcount_t *s)
{
unsigned ret = __read_seqcount_begin(s);
smp_rmb();
return ret;
}
static inline unsigned raw_seqcount_begin(const seqcount_t *s)
{
unsigned ret = ACCESS_ONCE(s->sequence);
smp_rmb();
return ret & ~1;
}
static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
{
return unlikely(s->sequence != start);
}
static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
{
smp_rmb();
return __read_seqcount_retry(s, start);
}
static inline void write_seqcount_begin(seqcount_t *s)
{
s->sequence++;
smp_wmb();
}
static inline void write_seqcount_end(seqcount_t *s)
{
smp_wmb();
s->sequence++;
}
static inline void write_seqcount_barrier(seqcount_t *s)
{
smp_wmb();
s->sequence+=2;
}
#define write_seqlock_irqsave(lock, flags) \
do { local_irq_save(flags); write_seqlock(lock); } while (0)
#define write_seqlock_irq(lock) \
do { local_irq_disable(); write_seqlock(lock); } while (0)
#define write_seqlock_bh(lock) \
do { local_bh_disable(); write_seqlock(lock); } while (0)
#define write_sequnlock_irqrestore(lock, flags) \
do { write_sequnlock(lock); local_irq_restore(flags); } while(0)
#define write_sequnlock_irq(lock) \
do { write_sequnlock(lock); local_irq_enable(); } while(0)
#define write_sequnlock_bh(lock) \
do { write_sequnlock(lock); local_bh_enable(); } while(0)
#define read_seqbegin_irqsave(lock, flags) \
({ local_irq_save(flags); read_seqbegin(lock); })
#define read_seqretry_irqrestore(lock, iv, flags) \
({ \
int ret = read_seqretry(lock, iv); \
local_irq_restore(flags); \
ret; \
})
#endif
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