seqlock.h

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#pragma once
 
#include <kernel/sync/lock.h>
 
#include <stdatomic.h>
 
typedef struct
{
    atomic_uint64_t sequence;
    lock_t writeLock;
} seqlock_t;
 
#define SEQLOCK_CREATE {.sequence = ATOMIC_VAR_INIT(0), .writeLock = LOCK_CREATE}
 
static inline void seqlock_init(seqlock_t* seqlock)
{
    atomic_init(&seqlock->sequence, 0);
    lock_init(&seqlock->writeLock);
}
 
static inline void seqlock_write_acquire(seqlock_t* seqlock)
{
    lock_acquire(&seqlock->writeLock);
    atomic_fetch_add_explicit(&seqlock->sequence, 1, memory_order_acquire);
}
 
static inline void seqlock_write_release(seqlock_t* seqlock)
{
    atomic_fetch_add_explicit(&seqlock->sequence, 1, memory_order_release);
    lock_release(&seqlock->writeLock);
}
 
static inline uint64_t seqlock_read_begin(seqlock_t* seqlock)
{
    return atomic_load_explicit(&seqlock->sequence, memory_order_acquire);
}
 
static inline bool seqlock_read_retry(seqlock_t* seqlock, uint64_t seq)
{
    atomic_thread_fence(memory_order_acquire);
    return (atomic_load_explicit(&seqlock->sequence, memory_order_relaxed) != seq) || (seq & 1);
}