690141ff8b
This implementation does not use locking or condition variables internally; it's purely based on atomics and futexes. Notably, concurrent sem_wait() and sem_post() calls can run *completely in parallel* without slowing each other down, as long as there are empty slots for them all to succeed without blocking. Additionally, sem_wait() never executes an atomic operation with release ordering, and sem_post() never executes an atomic operation with acquire ordering (unless you count the syscall). This means the compiler and the hardware are free to reorder code *into* the critical section.
33 lines
628 B
C
33 lines
628 B
C
/*
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* Copyright (c) 2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <limits.h>
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#include <pthread.h>
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#include <sys/cdefs.h>
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#include <sys/types.h>
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__BEGIN_DECLS
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typedef struct {
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uint32_t value;
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} sem_t;
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int sem_close(sem_t*);
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int sem_destroy(sem_t*);
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int sem_getvalue(sem_t*, int*);
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int sem_init(sem_t*, int, unsigned int);
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sem_t* sem_open(const char*, int, ...);
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int sem_post(sem_t*);
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int sem_trywait(sem_t*);
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int sem_unlink(const char*);
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int sem_wait(sem_t*);
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int sem_timedwait(sem_t*, const struct timespec* abstime);
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#define SEM_VALUE_MAX INT_MAX
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__END_DECLS
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