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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [UNIKRAFT PATCH, v2, 01/15] lib/ukring: Import simple ring buffer from FreeBSD
Copied as it is from the official FreeBSD git mirror. Commit: c45cce178ce658f81901a45c741b7f3c47ce2250 - https://github.com/freebsd/freebsd/blob/c45cce1/sys/sys/buf_ring.h - https://github.com/freebsd/freebsd/blob/c45cce1/sys/kern/subr_bufring.c Signed-off-by: Alexander Jung <alexander.jung@xxxxxxxxx> --- lib/ukring/include/uk/ring.h | 371 +++++++++++++++++++++++++++++++++++ lib/ukring/ring.c | 65 ++++++ 2 files changed, 436 insertions(+) create mode 100644 lib/ukring/include/uk/ring.h create mode 100644 lib/ukring/ring.c diff --git a/lib/ukring/include/uk/ring.h b/lib/ukring/include/uk/ring.h new file mode 100644 index 0000000..899563c --- /dev/null +++ b/lib/ukring/include/uk/ring.h @@ -0,0 +1,371 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * Copyright (c) 2007-2009 Kip Macy <kmacy@xxxxxxxxxxx> + * All rights reserved. + * + * 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. + * + * $FreeBSD$ + * + */ + +#ifndef _SYS_BUF_RING_H_ +#define _SYS_BUF_RING_H_ + +#include <machine/cpu.h> + +#ifdef DEBUG_BUFRING +#include <sys/lock.h> +#include <sys/mutex.h> +#endif + +struct buf_ring { + volatile uint32_t br_prod_head; + volatile uint32_t br_prod_tail; + int br_prod_size; + int br_prod_mask; + uint64_t br_drops; + volatile uint32_t br_cons_head __aligned(CACHE_LINE_SIZE); + volatile uint32_t br_cons_tail; + int br_cons_size; + int br_cons_mask; +#ifdef DEBUG_BUFRING + struct mtx *br_lock; +#endif + void *br_ring[0] __aligned(CACHE_LINE_SIZE); +}; + +/* + * multi-producer safe lock-free ring buffer enqueue + * + */ +static __inline int +buf_ring_enqueue(struct buf_ring *br, void *buf) +{ + uint32_t prod_head, prod_next, cons_tail; +#ifdef DEBUG_BUFRING + int i; + + /* + * Note: It is possible to encounter an mbuf that was removed + * via drbr_peek(), and then re-added via drbr_putback() and + * trigger a spurious panic. + */ + for (i = br->br_cons_head; i != br->br_prod_head; + i = ((i + 1) & br->br_cons_mask)) + if(br->br_ring[i] == buf) + panic("buf=%p already enqueue at %d prod=%d cons=%d", + buf, i, br->br_prod_tail, br->br_cons_tail); +#endif + critical_enter(); + do { + prod_head = br->br_prod_head; + prod_next = (prod_head + 1) & br->br_prod_mask; + cons_tail = br->br_cons_tail; + + if (prod_next == cons_tail) { + rmb(); + if (prod_head == br->br_prod_head && + cons_tail == br->br_cons_tail) { + br->br_drops++; + critical_exit(); + return (ENOBUFS); + } + continue; + } + } while (!atomic_cmpset_acq_int(&br->br_prod_head, prod_head, prod_next)); +#ifdef DEBUG_BUFRING + if (br->br_ring[prod_head] != NULL) + panic("dangling value in enqueue"); +#endif + br->br_ring[prod_head] = buf; + + /* + * If there are other enqueues in progress + * that preceded us, we need to wait for them + * to complete + */ + while (br->br_prod_tail != prod_head) + cpu_spinwait(); + atomic_store_rel_int(&br->br_prod_tail, prod_next); + critical_exit(); + return (0); +} + +/* + * multi-consumer safe dequeue + * + */ +static __inline void * +buf_ring_dequeue_mc(struct buf_ring *br) +{ + uint32_t cons_head, cons_next; + void *buf; + + critical_enter(); + do { + cons_head = br->br_cons_head; + cons_next = (cons_head + 1) & br->br_cons_mask; + + if (cons_head == br->br_prod_tail) { + critical_exit(); + return (NULL); + } + } while (!atomic_cmpset_acq_int(&br->br_cons_head, cons_head, cons_next)); + + buf = br->br_ring[cons_head]; +#ifdef DEBUG_BUFRING + br->br_ring[cons_head] = NULL; +#endif + /* + * If there are other dequeues in progress + * that preceded us, we need to wait for them + * to complete + */ + while (br->br_cons_tail != cons_head) + cpu_spinwait(); + + atomic_store_rel_int(&br->br_cons_tail, cons_next); + critical_exit(); + + return (buf); +} + +/* + * single-consumer dequeue + * use where dequeue is protected by a lock + * e.g. a network driver's tx queue lock + */ +static __inline void * +buf_ring_dequeue_sc(struct buf_ring *br) +{ + uint32_t cons_head, cons_next; +#ifdef PREFETCH_DEFINED + uint32_t cons_next_next; +#endif + uint32_t prod_tail; + void *buf; + + /* + * This is a workaround to allow using buf_ring on ARM and ARM64. + * ARM64TODO: Fix buf_ring in a generic way. + * REMARKS: It is suspected that br_cons_head does not require + * load_acq operation, but this change was extensively tested + * and confirmed it's working. To be reviewed once again in + * FreeBSD-12. + * + * Preventing following situation: + * Core(0) - buf_ring_enqueue() Core(1) - buf_ring_dequeue_sc() + * ----------------------------------------- ---------------------------------------------- + * + * cons_head = br->br_cons_head; + * atomic_cmpset_acq_32(&br->br_prod_head, ...)); + * buf = br->br_ring[cons_head]; <see <1>> + * br->br_ring[prod_head] = buf; + * atomic_store_rel_32(&br->br_prod_tail, ...); + * prod_tail = br->br_prod_tail; + * if (cons_head == prod_tail) + * return (NULL); + * <condition is false and code uses invalid(old) buf>` + * + * <1> Load (on core 1) from br->br_ring[cons_head] can be reordered (speculative readed) by CPU. + */ +#if defined(__arm__) || defined(__aarch64__) + cons_head = atomic_load_acq_32(&br->br_cons_head); +#else + cons_head = br->br_cons_head; +#endif + prod_tail = atomic_load_acq_32(&br->br_prod_tail); + + cons_next = (cons_head + 1) & br->br_cons_mask; +#ifdef PREFETCH_DEFINED + cons_next_next = (cons_head + 2) & br->br_cons_mask; +#endif + + if (cons_head == prod_tail) + return (NULL); + +#ifdef PREFETCH_DEFINED + if (cons_next != prod_tail) { + prefetch(br->br_ring[cons_next]); + if (cons_next_next != prod_tail) + prefetch(br->br_ring[cons_next_next]); + } +#endif + br->br_cons_head = cons_next; + buf = br->br_ring[cons_head]; + +#ifdef DEBUG_BUFRING + br->br_ring[cons_head] = NULL; + if (!mtx_owned(br->br_lock)) + panic("lock not held on single consumer dequeue"); + if (br->br_cons_tail != cons_head) + panic("inconsistent list cons_tail=%d cons_head=%d", + br->br_cons_tail, cons_head); +#endif + br->br_cons_tail = cons_next; + return (buf); +} + +/* + * single-consumer advance after a peek + * use where it is protected by a lock + * e.g. a network driver's tx queue lock + */ +static __inline void +buf_ring_advance_sc(struct buf_ring *br) +{ + uint32_t cons_head, cons_next; + uint32_t prod_tail; + + cons_head = br->br_cons_head; + prod_tail = br->br_prod_tail; + + cons_next = (cons_head + 1) & br->br_cons_mask; + if (cons_head == prod_tail) + return; + br->br_cons_head = cons_next; +#ifdef DEBUG_BUFRING + br->br_ring[cons_head] = NULL; +#endif + br->br_cons_tail = cons_next; +} + +/* + * Used to return a buffer (most likely already there) + * to the top of the ring. The caller should *not* + * have used any dequeue to pull it out of the ring + * but instead should have used the peek() function. + * This is normally used where the transmit queue + * of a driver is full, and an mbuf must be returned. + * Most likely whats in the ring-buffer is what + * is being put back (since it was not removed), but + * sometimes the lower transmit function may have + * done a pullup or other function that will have + * changed it. As an optimization we always put it + * back (since jhb says the store is probably cheaper), + * if we have to do a multi-queue version we will need + * the compare and an atomic. + */ +static __inline void +buf_ring_putback_sc(struct buf_ring *br, void *new) +{ + KASSERT(br->br_cons_head != br->br_prod_tail, + ("Buf-Ring has none in putback")) ; + br->br_ring[br->br_cons_head] = new; +} + +/* + * return a pointer to the first entry in the ring + * without modifying it, or NULL if the ring is empty + * race-prone if not protected by a lock + */ +static __inline void * +buf_ring_peek(struct buf_ring *br) +{ + +#ifdef DEBUG_BUFRING + if ((br->br_lock != NULL) && !mtx_owned(br->br_lock)) + panic("lock not held on single consumer dequeue"); +#endif + /* + * I believe it is safe to not have a memory barrier + * here because we control cons and tail is worst case + * a lagging indicator so we worst case we might + * return NULL immediately after a buffer has been enqueued + */ + if (br->br_cons_head == br->br_prod_tail) + return (NULL); + + return (br->br_ring[br->br_cons_head]); +} + +static __inline void * +buf_ring_peek_clear_sc(struct buf_ring *br) +{ +#ifdef DEBUG_BUFRING + void *ret; + + if (!mtx_owned(br->br_lock)) + panic("lock not held on single consumer dequeue"); +#endif + + if (br->br_cons_head == br->br_prod_tail) + return (NULL); + +#if defined(__arm__) || defined(__aarch64__) + /* + * The barrier is required there on ARM and ARM64 to ensure, that + * br->br_ring[br->br_cons_head] will not be fetched before the above + * condition is checked. + * Without the barrier, it is possible, that buffer will be fetched + * before the enqueue will put mbuf into br, then, in the meantime, the + * enqueue will update the array and the br_prod_tail, and the + * conditional check will be true, so we will return previously fetched + * (and invalid) buffer. + */ + atomic_thread_fence_acq(); +#endif + +#ifdef DEBUG_BUFRING + /* + * Single consumer, i.e. cons_head will not move while we are + * running, so atomic_swap_ptr() is not necessary here. + */ + ret = br->br_ring[br->br_cons_head]; + br->br_ring[br->br_cons_head] = NULL; + return (ret); +#else + return (br->br_ring[br->br_cons_head]); +#endif +} + +static __inline int +buf_ring_full(struct buf_ring *br) +{ + + return (((br->br_prod_head + 1) & br->br_prod_mask) == br->br_cons_tail); +} + +static __inline int +buf_ring_empty(struct buf_ring *br) +{ + + return (br->br_cons_head == br->br_prod_tail); +} + +static __inline int +buf_ring_count(struct buf_ring *br) +{ + + return ((br->br_prod_size + br->br_prod_tail - br->br_cons_tail) + & br->br_prod_mask); +} + +struct buf_ring *buf_ring_alloc(int count, struct malloc_type *type, int flags, + struct mtx *); +void buf_ring_free(struct buf_ring *br, struct malloc_type *type); + + + +#endif \ No newline at end of file diff --git a/lib/ukring/ring.c b/lib/ukring/ring.c new file mode 100644 index 0000000..644c3be --- /dev/null +++ b/lib/ukring/ring.c @@ -0,0 +1,65 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause-FreeBSD + * + * Copyright (c) 2007, 2008 Kip Macy <kmacy@xxxxxxxxxxx> + * All rights reserved. + * + * 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. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/malloc.h> +#include <sys/ktr.h> +#include <sys/buf_ring.h> + +struct buf_ring * +buf_ring_alloc(int count, struct malloc_type *type, int flags, struct mtx *lock) +{ + struct buf_ring *br; + + KASSERT(powerof2(count), ("buf ring must be size power of 2")); + + br = malloc(sizeof(struct buf_ring) + count*sizeof(caddr_t), + type, flags|M_ZERO); + if (br == NULL) + return (NULL); +#ifdef DEBUG_BUFRING + br->br_lock = lock; +#endif + br->br_prod_size = br->br_cons_size = count; + br->br_prod_mask = br->br_cons_mask = count-1; + br->br_prod_head = br->br_cons_head = 0; + br->br_prod_tail = br->br_cons_tail = 0; + + return (br); +} + +void +buf_ring_free(struct buf_ring *br, struct malloc_type *type) +{ + free(br, type); +} \ No newline at end of file -- 2.20.1
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