Zephyr API Documentation
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spsc_lockfree.h
Go to the documentation of this file.
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/*
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* Copyright (c) 2023 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_SYS_SPSC_LOCKFREE_H_
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#define ZEPHYR_SYS_SPSC_LOCKFREE_H_
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#include <
stdint.h
>
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#include <
stdbool.h
>
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#include <
zephyr/toolchain/common.h
>
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#include <
zephyr/sys/atomic.h
>
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#include <
zephyr/sys/util_macro.h
>
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struct
spsc {
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/* private value only the producer thread should mutate */
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unsigned
long
acquire;
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/* private value only the consumer thread should mutate */
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unsigned
long
consume;
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/* producer mutable, consumer readable */
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atomic_t
in;
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/* consumer mutable, producer readable */
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atomic_t
out;
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/* mask used to automatically wrap values */
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const
unsigned
long
mask;
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};
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#define SPSC_INITIALIZER(sz, buf) \
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{ \
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._spsc = \
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{ \
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.acquire = 0, \
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.consume = 0, \
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.in = ATOMIC_INIT(0), \
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.out = ATOMIC_INIT(0), \
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.mask = sz - 1, \
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}, \
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.buffer = buf, \
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}
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#define SPSC_DECLARE(name, type) \
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static struct spsc_##name { \
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struct spsc _spsc; \
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type * const buffer; \
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}
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#define SPSC_DEFINE(name, type, sz) \
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BUILD_ASSERT(IS_POWER_OF_TWO(sz)); \
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static type __spsc_buf_##name[sz]; \
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SPSC_DECLARE(name, type) name = SPSC_INITIALIZER(sz, __spsc_buf_##name);
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#define spsc_size(spsc) ((spsc)->_spsc.mask + 1)
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#define z_spsc_mask(spsc, i) ((i) & (spsc)->_spsc.mask)
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#define z_spsc_in(spsc) (unsigned long)atomic_get(&(spsc)->_spsc.in)
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#define z_spsc_out(spsc) (unsigned long)atomic_get(&(spsc)->_spsc.out)
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#define spsc_reset(spsc) \
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({ \
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(spsc)->_spsc.consume = 0; \
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(spsc)->_spsc.acquire = 0; \
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atomic_set(&(spsc)->_spsc.in, 0); \
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atomic_set(&(spsc)->_spsc.out, 0); \
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})
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#define spsc_acquire(spsc) \
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({ \
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unsigned long idx = z_spsc_in(spsc) + (spsc)->_spsc.acquire; \
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bool spsc_acq = (idx - z_spsc_out(spsc)) < spsc_size(spsc); \
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if (spsc_acq) { \
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(spsc)->_spsc.acquire += 1; \
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} \
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spsc_acq ? &((spsc)->buffer[z_spsc_mask(spsc, idx)]) : NULL; \
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})
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#define spsc_produce(spsc) \
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({ \
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if ((spsc)->_spsc.acquire > 0) { \
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(spsc)->_spsc.acquire -= 1; \
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atomic_add(&(spsc)->_spsc.in, 1); \
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} \
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})
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#define spsc_produce_all(spsc) \
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({ \
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if ((spsc)->_spsc.acquire > 0) { \
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unsigned long acquired = (spsc)->_spsc.acquire; \
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(spsc)->_spsc.acquire = 0; \
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atomic_add(&(spsc)->_spsc.in, acquired); \
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} \
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})
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#define spsc_drop_all(spsc) \
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do { \
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(spsc)->_spsc.acquire = 0; \
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} while (false)
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#define spsc_consume(spsc) \
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({ \
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unsigned long idx = z_spsc_out(spsc) + (spsc)->_spsc.consume; \
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bool has_consumable = (idx != z_spsc_in(spsc)); \
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if (has_consumable) { \
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(spsc)->_spsc.consume += 1; \
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} \
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has_consumable ? &((spsc)->buffer[z_spsc_mask(spsc, idx)]) : NULL; \
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})
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#define spsc_release(spsc) \
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({ \
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if ((spsc)->_spsc.consume > 0) { \
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(spsc)->_spsc.consume -= 1; \
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atomic_add(&(spsc)->_spsc.out, 1); \
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} \
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})
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#define spsc_release_all(spsc) \
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({ \
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if ((spsc)->_spsc.consume > 0) { \
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unsigned long consumed = (spsc)->_spsc.consume; \
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(spsc)->_spsc.consume = 0; \
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atomic_add(&(spsc)->_spsc.out, consumed); \
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} \
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})
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#define spsc_acquirable(spsc) \
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({ (((spsc)->_spsc.in + (spsc)->_spsc.acquire) - (spsc)->_spsc.out) - spsc_size(spsc); })
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#define spsc_consumable(spsc) ({ (spsc)->_spsc.in - (spsc)->_spsc.out - (spsc)->_spsc.consume; })
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#define spsc_peek(spsc) \
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({ \
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unsigned long idx = z_spsc_out(spsc) + (spsc)->_spsc.consume; \
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bool has_consumable = (idx != z_spsc_in(spsc)); \
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has_consumable ? &((spsc)->buffer[z_spsc_mask(spsc, idx)]) : NULL; \
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})
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#define spsc_next(spsc, item) \
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({ \
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unsigned long idx = ((item) - (spsc)->buffer); \
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bool has_next = \
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z_spsc_mask(spsc, (idx + 1)) != (z_spsc_mask(spsc, z_spsc_in(spsc))); \
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has_next ? &((spsc)->buffer[z_spsc_mask((spsc), idx + 1)]) : NULL; \
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})
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#define spsc_prev(spsc, item) \
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({ \
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unsigned long idx = ((item) - &(spsc)->buffer[0]) / sizeof((spsc)->buffer[0]); \
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bool has_prev = idx != z_spsc_mask(spsc, z_spsc_out(spsc)); \
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has_prev ? &((spsc)->buffer[z_spsc_mask(spsc, idx - 1)]) : NULL; \
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})
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#endif
/* ZEPHYR_SYS_SPSC_LOCKFREE_H_ */
atomic_t
long atomic_t
Definition
atomic_types.h:15
common.h
Common toolchain abstraction.
stdbool.h
stdint.h
atomic.h
util_macro.h
Macro utilities.
zephyr
sys
spsc_lockfree.h
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