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322 lines
8.7 KiB
322 lines
8.7 KiB
/*
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* Copyright 2013-2014 Samy Al Bahra.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _CK_ELIDE_H
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#define _CK_ELIDE_H
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/*
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* As RTM is currently only supported on TSO x86 architectures,
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* fences have been omitted. They will be necessary for other
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* non-TSO architectures with TM support.
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*/
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#include <ck_cc.h>
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#include <ck_pr.h>
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#include <string.h>
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/*
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* skip_-prefixed counters represent the number of consecutive
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* elisions to forfeit. retry_-prefixed counters represent the
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* number of elision retries to attempt before forfeit.
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*
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* _busy: Lock was busy
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* _other: Unknown explicit abort
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* _conflict: Data conflict in elision section
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*/
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struct ck_elide_config {
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unsigned short skip_busy;
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short retry_busy;
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unsigned short skip_other;
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short retry_other;
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unsigned short skip_conflict;
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short retry_conflict;
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};
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#define CK_ELIDE_CONFIG_DEFAULT_INITIALIZER { \
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.skip_busy = 5, \
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.retry_busy = 256, \
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.skip_other = 3, \
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.retry_other = 3, \
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.skip_conflict = 2, \
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.retry_conflict = 5 \
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}
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struct ck_elide_stat {
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unsigned int n_fallback;
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unsigned int n_elide;
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unsigned short skip;
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};
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typedef struct ck_elide_stat ck_elide_stat_t;
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#define CK_ELIDE_STAT_INITIALIZER { 0, 0, 0 }
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static inline void
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ck_elide_stat_init(ck_elide_stat_t *st)
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{
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memset(st, 0, sizeof(*st));
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return;
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}
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#ifdef CK_F_PR_RTM
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enum _ck_elide_hint {
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CK_ELIDE_HINT_RETRY = 0,
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CK_ELIDE_HINT_SPIN,
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CK_ELIDE_HINT_STOP
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};
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#define _CK_ELIDE_LOCK_BUSY 0xFF
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static enum _ck_elide_hint
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_ck_elide_fallback(int *retry,
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struct ck_elide_stat *st,
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struct ck_elide_config *c,
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unsigned int status)
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{
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st->n_fallback++;
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if (*retry > 0)
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return CK_ELIDE_HINT_RETRY;
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if (st->skip != 0)
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return CK_ELIDE_HINT_STOP;
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if (status & CK_PR_RTM_EXPLICIT) {
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if (CK_PR_RTM_CODE(status) == _CK_ELIDE_LOCK_BUSY) {
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st->skip = c->skip_busy;
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*retry = c->retry_busy;
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return CK_ELIDE_HINT_SPIN;
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}
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st->skip = c->skip_other;
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return CK_ELIDE_HINT_STOP;
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}
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if ((status & CK_PR_RTM_RETRY) &&
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(status & CK_PR_RTM_CONFLICT)) {
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st->skip = c->skip_conflict;
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*retry = c->retry_conflict;
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return CK_ELIDE_HINT_RETRY;
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}
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/*
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* Capacity, debug and nesting abortions are likely to be
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* invariant conditions for the acquisition, execute regular
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* path instead. If retry bit is not set, then take the hint.
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*/
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st->skip = USHRT_MAX;
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return CK_ELIDE_HINT_STOP;
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}
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/*
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* Defines an elision implementation according to the following variables:
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* N - Namespace of elision implementation.
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* T - Typename of mutex.
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* L_P - Lock predicate, returns false if resource is available.
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* L - Function to call if resource is unavailable of transaction aborts.
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* U_P - Unlock predicate, returns false if elision failed.
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* U - Function to call if transaction failed.
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*/
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#define CK_ELIDE_PROTOTYPE(N, T, L_P, L, U_P, U) \
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CK_CC_INLINE static void \
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ck_elide_##N##_lock_adaptive(T *lock, \
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struct ck_elide_stat *st, \
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struct ck_elide_config *c) \
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{ \
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enum _ck_elide_hint hint; \
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int retry; \
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\
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if (CK_CC_UNLIKELY(st->skip != 0)) { \
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st->skip--; \
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goto acquire; \
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} \
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\
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retry = c->retry_conflict; \
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do { \
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unsigned int status = ck_pr_rtm_begin(); \
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if (status == CK_PR_RTM_STARTED) { \
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if (L_P(lock) == true) \
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ck_pr_rtm_abort(_CK_ELIDE_LOCK_BUSY); \
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\
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return; \
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} \
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\
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hint = _ck_elide_fallback(&retry, st, c, status); \
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if (hint == CK_ELIDE_HINT_RETRY) \
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continue; \
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\
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if (hint == CK_ELIDE_HINT_SPIN) { \
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while (--retry != 0) { \
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if (L_P(lock) == false) \
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break; \
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\
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ck_pr_stall(); \
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} \
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\
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continue; \
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} \
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\
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if (hint == CK_ELIDE_HINT_STOP) \
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break; \
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} while (CK_CC_LIKELY(--retry > 0)); \
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\
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acquire: \
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L(lock); \
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_unlock_adaptive(struct ck_elide_stat *st, T *lock) \
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{ \
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\
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if (U_P(lock) == false) { \
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ck_pr_rtm_end(); \
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st->skip = 0; \
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st->n_elide++; \
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} else { \
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U(lock); \
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} \
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\
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_lock(T *lock) \
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{ \
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\
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if (ck_pr_rtm_begin() != CK_PR_RTM_STARTED) { \
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L(lock); \
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return; \
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} \
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\
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if (L_P(lock) == true) \
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ck_pr_rtm_abort(_CK_ELIDE_LOCK_BUSY); \
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\
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_unlock(T *lock) \
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{ \
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\
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if (U_P(lock) == false) { \
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ck_pr_rtm_end(); \
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} else { \
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U(lock); \
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} \
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\
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return; \
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}
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#define CK_ELIDE_TRYLOCK_PROTOTYPE(N, T, TL_P, TL) \
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CK_CC_INLINE static bool \
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ck_elide_##N##_trylock(T *lock) \
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{ \
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\
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if (ck_pr_rtm_begin() != CK_PR_RTM_STARTED) \
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return false; \
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\
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if (TL_P(lock) == true) \
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ck_pr_rtm_abort(_CK_ELIDE_LOCK_BUSY); \
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\
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return true; \
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}
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#else
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/*
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* If RTM is not enabled on the target platform (CK_F_PR_RTM) then these
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* elision wrappers directly calls into the user-specified lock operations.
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* Unfortunately, the storage cost of both ck_elide_config and ck_elide_stat
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* are paid (typically a storage cost that is a function of lock objects and
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* thread count).
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*/
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#define CK_ELIDE_PROTOTYPE(N, T, L_P, L, U_P, U) \
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CK_CC_INLINE static void \
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ck_elide_##N##_lock_adaptive(T *lock, \
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struct ck_elide_stat *st, \
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struct ck_elide_config *c) \
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{ \
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\
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(void)st; \
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(void)c; \
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L(lock); \
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_unlock_adaptive(struct ck_elide_stat *st, \
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T *lock) \
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{ \
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\
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(void)st; \
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U(lock); \
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_lock(T *lock) \
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{ \
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\
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L(lock); \
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return; \
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} \
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CK_CC_INLINE static void \
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ck_elide_##N##_unlock(T *lock) \
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{ \
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\
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U(lock); \
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return; \
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}
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#define CK_ELIDE_TRYLOCK_PROTOTYPE(N, T, TL_P, TL) \
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CK_CC_INLINE static bool \
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ck_elide_##N##_trylock(T *lock) \
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{ \
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\
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return TL_P(lock); \
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}
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#endif /* !CK_F_PR_RTM */
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/*
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* Best-effort elision lock operations. First argument is name (N)
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* associated with implementation and the second is a pointer to
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* the type specified above (T).
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*
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* Unlike the adaptive variant, this interface does not have any retry
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* semantics. In environments where jitter is low, this may yield a tighter
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* fast path.
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*/
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#define CK_ELIDE_LOCK(NAME, LOCK) ck_elide_##NAME##_lock(LOCK)
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#define CK_ELIDE_UNLOCK(NAME, LOCK) ck_elide_##NAME##_unlock(LOCK)
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#define CK_ELIDE_TRYLOCK(NAME, LOCK) ck_elide_##NAME##_trylock(LOCK)
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/*
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* Adaptive elision lock operations. In addition to name and pointer
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* to the lock, you must pass in a pointer to an initialized
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* ck_elide_config structure along with a per-thread stat structure.
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*/
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#define CK_ELIDE_LOCK_ADAPTIVE(NAME, STAT, CONFIG, LOCK) \
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ck_elide_##NAME##_lock_adaptive(LOCK, STAT, CONFIG)
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#define CK_ELIDE_UNLOCK_ADAPTIVE(NAME, STAT, LOCK) \
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ck_elide_##NAME##_unlock_adaptive(STAT, LOCK)
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#endif /* _CK_ELIDE_H */
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