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243 lines
8.9 KiB
C++
243 lines
8.9 KiB
C++
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
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/* Fair readers writer lock implemented using condition variables.
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* This is maintained so that we can measure the performance of a relatively simple implementation (this one)
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* compared to a fast one that uses compare-and-swap (the one in ../toku_rwlock.c)
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*/
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#ident "$Id$"
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/*
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COPYING CONDITIONS NOTICE:
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This program is free software; you can redistribute it and/or modify
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it under the terms of version 2 of the GNU General Public License as
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published by the Free Software Foundation, and provided that the
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following conditions are met:
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* Redistributions of source code must retain this COPYING
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CONDITIONS NOTICE, the COPYRIGHT NOTICE (below), the
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DISCLAIMER (below), the UNIVERSITY PATENT NOTICE (below), the
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PATENT MARKING NOTICE (below), and the PATENT RIGHTS
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GRANT (below).
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* Redistributions in binary form must reproduce this COPYING
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CONDITIONS NOTICE, the COPYRIGHT NOTICE (below), the
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DISCLAIMER (below), the UNIVERSITY PATENT NOTICE (below), the
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PATENT MARKING NOTICE (below), and the PATENT RIGHTS
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GRANT (below) in the documentation and/or other materials
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provided with the distribution.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301, USA.
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COPYRIGHT NOTICE:
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TokuDB, Tokutek Fractal Tree Indexing Library.
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Copyright (C) 2007-2013 Tokutek, Inc.
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DISCLAIMER:
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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UNIVERSITY PATENT NOTICE:
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The technology is licensed by the Massachusetts Institute of
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Technology, Rutgers State University of New Jersey, and the Research
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Foundation of State University of New York at Stony Brook under
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United States of America Serial No. 11/760379 and to the patents
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and/or patent applications resulting from it.
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PATENT MARKING NOTICE:
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This software is covered by US Patent No. 8,185,551.
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PATENT RIGHTS GRANT:
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"THIS IMPLEMENTATION" means the copyrightable works distributed by
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Tokutek as part of the Fractal Tree project.
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"PATENT CLAIMS" means the claims of patents that are owned or
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licensable by Tokutek, both currently or in the future; and that in
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the absence of this license would be infringed by THIS
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IMPLEMENTATION or by using or running THIS IMPLEMENTATION.
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"PATENT CHALLENGE" shall mean a challenge to the validity,
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patentability, enforceability and/or non-infringement of any of the
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PATENT CLAIMS or otherwise opposing any of the PATENT CLAIMS.
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Tokutek hereby grants to you, for the term and geographical scope of
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the PATENT CLAIMS, a non-exclusive, no-charge, royalty-free,
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irrevocable (except as stated in this section) patent license to
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make, have made, use, offer to sell, sell, import, transfer, and
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otherwise run, modify, and propagate the contents of THIS
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IMPLEMENTATION, where such license applies only to the PATENT
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CLAIMS. This grant does not include claims that would be infringed
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only as a consequence of further modifications of THIS
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IMPLEMENTATION. If you or your agent or licensee institute or order
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or agree to the institution of patent litigation against any entity
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(including a cross-claim or counterclaim in a lawsuit) alleging that
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THIS IMPLEMENTATION constitutes direct or contributory patent
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infringement, or inducement of patent infringement, then any rights
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granted to you under this License shall terminate as of the date
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such litigation is filed. If you or your agent or exclusive
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licensee institute or order or agree to the institution of a PATENT
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CHALLENGE, then Tokutek may terminate any rights granted to you
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under this License.
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*/
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#ident "Copyright (c) 2010-2013 Tokutek Inc. All rights reserved."
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// Fair readers/writer locks. These are fair (meaning first-come first-served. No reader starvation, and no writer starvation). And they are
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// probably faster than the linux readers/writer locks (pthread_rwlock_t).
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struct toku_cv_fair_rwlock_waiter_state; // this structure is used internally.
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typedef struct toku_cv_fair_rwlock_s {
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toku_mutex_t mutex;
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int state; // 0 means no locks, + is number of readers locked, -1 is a writer
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struct toku_cv_fair_rwlock_waiter_state *waiters_head, *waiters_tail;
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} toku_cv_fair_rwlock_t;
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int toku_cv_fair_rwlock_init (toku_cv_fair_rwlock_t *rwlock);
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int toku_cv_fair_rwlock_destroy (toku_cv_fair_rwlock_t *rwlock);
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int toku_cv_fair_rwlock_rdlock (toku_cv_fair_rwlock_t *rwlock);
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int toku_cv_fair_rwlock_wrlock (toku_cv_fair_rwlock_t *rwlock);
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int toku_cv_fair_rwlock_unlock (toku_cv_fair_rwlock_t *rwlock);
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struct toku_cv_fair_rwlock_waiter_state {
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char is_read;
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struct toku_cv_fair_rwlock_waiter_state *next;
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toku_cond_t cond;
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};
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#if defined(HAVE_GNU_TLS)
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static __thread struct toku_cv_fair_rwlock_waiter_state waitstate_var = {0, NULL, { PTHREAD_COND_INITIALIZER } };
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#define GET_WAITSTATE(name) name = &waitstate_var
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#else
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#include <memory.h>
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static pthread_key_t waitstate_key;
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static bool waitstate_key_initialized = false;
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void
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toku_rwlock_init(void)
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{
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assert(!waitstate_key_initialized);
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int r = toku_pthread_key_create(&waitstate_key, toku_free);
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assert_zero(r);
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waitstate_key_initialized = true;
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}
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void
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toku_rwlock_destroy(void)
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{
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assert(waitstate_key_initialized);
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int r = toku_pthread_key_delete(waitstate_key);
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assert_zero(r);
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waitstate_key_initialized = false;
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}
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static struct toku_cv_fair_rwlock_waiter_state *
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get_waitstate(void)
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{
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assert(waitstate_key_initialized);
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struct toku_cv_fair_rwlock_waiter_state *waitstate = NULL;
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void *p = toku_pthread_getspecific(waitstate_key);
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if (!p) {
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p = toku_xmalloc(sizeof *waitstate);
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int r = toku_pthread_setspecific(waitstate_key, p);
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assert_zero(r);
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}
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waitstate = static_cast<struct toku_cv_fair_rwlock_waiter_state *>(p);
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return waitstate;
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}
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#define GET_WAITSTATE(name) name = get_waitstate()
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#endif
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int toku_cv_fair_rwlock_init (toku_cv_fair_rwlock_t *rwlock) {
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rwlock->state=0;
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rwlock->waiters_head = NULL;
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rwlock->waiters_tail = NULL;
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toku_mutex_init(&rwlock->mutex, NULL);
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return 0;
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}
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int toku_cv_fair_rwlock_destroy (toku_cv_fair_rwlock_t *rwlock) {
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toku_mutex_destroy(&rwlock->mutex);
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return 0;
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}
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int toku_cv_fair_rwlock_rdlock (toku_cv_fair_rwlock_t *rwlock) {
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struct toku_cv_fair_rwlock_waiter_state *GET_WAITSTATE(waitstate);
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toku_mutex_lock(&rwlock->mutex);
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if (rwlock->waiters_head!=NULL || rwlock->state<0) {
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// Someone is ahead of me in the queue, or someone has a lock.
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// We use per-thread-state for the condition variable. A thread cannot get control and try to reuse the waiter state for something else.
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if (rwlock->waiters_tail) {
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rwlock->waiters_tail->next = waitstate;
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} else {
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rwlock->waiters_head = waitstate;
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}
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rwlock->waiters_tail = waitstate;
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waitstate->next = NULL;
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waitstate->is_read = 1;
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do {
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toku_cond_wait(&waitstate->cond, &rwlock->mutex);
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} while (rwlock->waiters_head!=waitstate || rwlock->state<0);
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rwlock->state++;
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rwlock->waiters_head=waitstate->next;
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if (waitstate->next==NULL) rwlock->waiters_tail=NULL;
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if (rwlock->waiters_head && rwlock->waiters_head->is_read) {
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toku_cond_signal(&rwlock->waiters_head->cond);
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}
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} else {
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// No one is waiting, and any holders are readers.
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rwlock->state++;
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}
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toku_mutex_unlock(&rwlock->mutex);
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return 0;
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}
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int toku_cv_fair_rwlock_wrlock (toku_cv_fair_rwlock_t *rwlock) {
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struct toku_cv_fair_rwlock_waiter_state *GET_WAITSTATE(waitstate);
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toku_mutex_lock(&rwlock->mutex);
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if (rwlock->waiters_head!=NULL || rwlock->state!=0) {
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// Someone else is ahead of me, or someone has a lock the lock, so we must wait our turn.
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if (rwlock->waiters_tail) {
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rwlock->waiters_tail->next = waitstate;
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} else {
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rwlock->waiters_head = waitstate;
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}
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rwlock->waiters_tail = waitstate;
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waitstate->next = NULL;
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waitstate->is_read = 0;
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do {
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toku_cond_wait(&waitstate->cond, &rwlock->mutex);
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} while (rwlock->waiters_head!=waitstate || rwlock->state!=0);
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rwlock->waiters_head = waitstate->next;
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if (waitstate->next==NULL) rwlock->waiters_tail=NULL;
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}
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rwlock->state = -1;
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toku_mutex_unlock(&rwlock->mutex);
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return 0;
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}
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int toku_cv_fair_rwlock_unlock (toku_cv_fair_rwlock_t *rwlock) {
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toku_mutex_lock(&rwlock->mutex);
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assert(rwlock->state!=0);
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if (rwlock->state>0) {
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rwlock->state--;
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} else {
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rwlock->state=0;
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}
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if (rwlock->state==0 && rwlock->waiters_head) {
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toku_cond_signal(&rwlock->waiters_head->cond);
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} else {
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// printf(" No one to wake\n");
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}
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toku_mutex_unlock(&rwlock->mutex);
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return 0;
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}
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