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Diffstat (limited to 'sys/contrib/ck/include/ck_bytelock.h')
| -rw-r--r-- | sys/contrib/ck/include/ck_bytelock.h | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/sys/contrib/ck/include/ck_bytelock.h b/sys/contrib/ck/include/ck_bytelock.h new file mode 100644 index 000000000000..d437316238b7 --- /dev/null +++ b/sys/contrib/ck/include/ck_bytelock.h @@ -0,0 +1,196 @@ +/* + * Copyright 2010-2015 Samy Al Bahra. + * 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. + */ + +#ifndef CK_BYTELOCK_H +#define CK_BYTELOCK_H + +/* + * The implementations here are derived from the work described in: + * Dice, D. and Shavit, N. 2010. TLRW: return of the read-write lock. + * In Proceedings of the 22nd ACM Symposium on Parallelism in Algorithms + * and Architectures (Thira, Santorini, Greece, June 13 - 15, 2010). + * SPAA '10. ACM, New York, NY, 284-293. + */ + +#include <ck_cc.h> +#include <ck_md.h> +#include <ck_pr.h> +#include <ck_stdbool.h> +#include <ck_stddef.h> +#include <ck_limits.h> + +struct ck_bytelock { + unsigned int owner; + unsigned int n_readers; + uint8_t readers[CK_MD_CACHELINE - sizeof(unsigned int) * 2] CK_CC_ALIGN(8); +}; +typedef struct ck_bytelock ck_bytelock_t; + +#define CK_BYTELOCK_INITIALIZER { 0, 0, {0} } +#define CK_BYTELOCK_UNSLOTTED UINT_MAX + +CK_CC_INLINE static void +ck_bytelock_init(struct ck_bytelock *bytelock) +{ + unsigned int i; + + bytelock->owner = 0; + bytelock->n_readers = 0; + for (i = 0; i < sizeof bytelock->readers; i++) + bytelock->readers[i] = false; + + ck_pr_barrier(); + return; +} + +#ifdef CK_F_PR_LOAD_64 +#define CK_BYTELOCK_LENGTH sizeof(uint64_t) +#define CK_BYTELOCK_LOAD ck_pr_load_64 +#define CK_BYTELOCK_TYPE uint64_t +#elif defined(CK_F_PR_LOAD_32) +#define CK_BYTELOCK_LENGTH sizeof(uint32_t) +#define CK_BYTELOCK_LOAD ck_pr_load_32 +#define CK_BYTELOCK_TYPE uint32_t +#else +#error Unsupported platform. +#endif + +CK_CC_INLINE static void +ck_bytelock_write_lock(struct ck_bytelock *bytelock, unsigned int slot) +{ + CK_BYTELOCK_TYPE *readers = (void *)bytelock->readers; + unsigned int i; + + /* Announce upcoming writer acquisition. */ + while (ck_pr_cas_uint(&bytelock->owner, 0, slot) == false) + ck_pr_stall(); + + /* If we are slotted, we might be upgrading from a read lock. */ + if (slot <= sizeof bytelock->readers) + ck_pr_store_8(&bytelock->readers[slot - 1], false); + + /* + * Wait for slotted readers to drain out. This also provides the + * lock acquire semantics. + */ + ck_pr_fence_atomic_load(); + + for (i = 0; i < sizeof(bytelock->readers) / CK_BYTELOCK_LENGTH; i++) { + while (CK_BYTELOCK_LOAD(&readers[i]) != false) + ck_pr_stall(); + } + + /* Wait for unslotted readers to drain out. */ + while (ck_pr_load_uint(&bytelock->n_readers) != 0) + ck_pr_stall(); + + ck_pr_fence_lock(); + return; +} + +#undef CK_BYTELOCK_LENGTH +#undef CK_BYTELOCK_LOAD +#undef CK_BYTELOCK_TYPE + +CK_CC_INLINE static void +ck_bytelock_write_unlock(struct ck_bytelock *bytelock) +{ + + ck_pr_fence_unlock(); + ck_pr_store_uint(&bytelock->owner, 0); + return; +} + +CK_CC_INLINE static void +ck_bytelock_read_lock(struct ck_bytelock *bytelock, unsigned int slot) +{ + + if (ck_pr_load_uint(&bytelock->owner) == slot) { + ck_pr_store_8(&bytelock->readers[slot - 1], true); + ck_pr_fence_strict_store(); + ck_pr_store_uint(&bytelock->owner, 0); + return; + } + + /* Unslotted threads will have to use the readers counter. */ + if (slot > sizeof bytelock->readers) { + for (;;) { + ck_pr_inc_uint(&bytelock->n_readers); + ck_pr_fence_atomic_load(); + if (ck_pr_load_uint(&bytelock->owner) == 0) + break; + ck_pr_dec_uint(&bytelock->n_readers); + + while (ck_pr_load_uint(&bytelock->owner) != 0) + ck_pr_stall(); + } + + ck_pr_fence_lock(); + return; + } + + slot -= 1; + for (;;) { +#ifdef CK_F_PR_FAA_8 + ck_pr_fas_8(&bytelock->readers[slot], true); + ck_pr_fence_atomic_load(); +#else + ck_pr_store_8(&bytelock->readers[slot], true); + ck_pr_fence_store_load(); +#endif + + /* + * If there is no owner at this point, our slot has + * already been published and it is guaranteed no + * write acquisition will succeed until we drain out. + */ + if (ck_pr_load_uint(&bytelock->owner) == 0) + break; + + ck_pr_store_8(&bytelock->readers[slot], false); + while (ck_pr_load_uint(&bytelock->owner) != 0) + ck_pr_stall(); + } + + ck_pr_fence_lock(); + return; +} + +CK_CC_INLINE static void +ck_bytelock_read_unlock(struct ck_bytelock *bytelock, unsigned int slot) +{ + + ck_pr_fence_unlock(); + + if (slot > sizeof bytelock->readers) + ck_pr_dec_uint(&bytelock->n_readers); + else + ck_pr_store_8(&bytelock->readers[slot - 1], false); + + return; +} + +#endif /* CK_BYTELOCK_H */ |