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Diffstat (limited to 'mysql/thr_rwlock.h')
| -rw-r--r-- | mysql/thr_rwlock.h | 214 |
1 files changed, 0 insertions, 214 deletions
diff --git a/mysql/thr_rwlock.h b/mysql/thr_rwlock.h deleted file mode 100644 index c177e29..0000000 --- a/mysql/thr_rwlock.h +++ /dev/null @@ -1,214 +0,0 @@ -#ifndef THR_RWLOCK_INCLUDED -#define THR_RWLOCK_INCLUDED - -/* Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved. - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; version 2 of the License. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ - -/** - MySQL rwlock implementation. - - There are two "layers": - 1) native_rw_*() - Functions that map directly down to OS primitives. - Windows - SRWLock - Other OSes - pthread - 2) mysql_rw*() - Functions that include Performance Schema instrumentation. - See include/mysql/psi/mysql_thread.h - - This file also includes rw_pr_*(), which implements a special - version of rwlocks that prefer readers. The P_S version of these - are mysql_prlock_*() - see include/mysql/psi/mysql_thread.h -*/ - -#include "my_global.h" -#include "my_thread.h" -#include "thr_cond.h" - -C_MODE_START - -#ifdef _WIN32 -typedef struct st_my_rw_lock_t -{ - SRWLOCK srwlock; /* native reader writer lock */ - BOOL have_exclusive_srwlock; /* used for unlock */ -} native_rw_lock_t; -#else -typedef pthread_rwlock_t native_rw_lock_t; -#endif - -static inline int native_rw_init(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - InitializeSRWLock(&rwp->srwlock); - rwp->have_exclusive_srwlock = FALSE; - return 0; -#else - /* pthread_rwlockattr_t is not used in MySQL */ - return pthread_rwlock_init(rwp, NULL); -#endif -} - -static inline int native_rw_destroy(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - return 0; /* no destroy function */ -#else - return pthread_rwlock_destroy(rwp); -#endif -} - -static inline int native_rw_rdlock(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - AcquireSRWLockShared(&rwp->srwlock); - return 0; -#else - return pthread_rwlock_rdlock(rwp); -#endif -} - -static inline int native_rw_tryrdlock(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - if (!TryAcquireSRWLockShared(&rwp->srwlock)) - return EBUSY; - return 0; -#else - return pthread_rwlock_tryrdlock(rwp); -#endif -} - -static inline int native_rw_wrlock(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - AcquireSRWLockExclusive(&rwp->srwlock); - rwp->have_exclusive_srwlock= TRUE; - return 0; -#else - return pthread_rwlock_wrlock(rwp); -#endif -} - -static inline int native_rw_trywrlock(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - if (!TryAcquireSRWLockExclusive(&rwp->srwlock)) - return EBUSY; - rwp->have_exclusive_srwlock= TRUE; - return 0; -#else - return pthread_rwlock_trywrlock(rwp); -#endif -} - -static inline int native_rw_unlock(native_rw_lock_t *rwp) -{ -#ifdef _WIN32 - if (rwp->have_exclusive_srwlock) - { - rwp->have_exclusive_srwlock= FALSE; - ReleaseSRWLockExclusive(&rwp->srwlock); - } - else - ReleaseSRWLockShared(&rwp->srwlock); - return 0; -#else - return pthread_rwlock_unlock(rwp); -#endif -} - - -/** - Portable implementation of special type of read-write locks. - - These locks have two properties which are unusual for rwlocks: - 1) They "prefer readers" in the sense that they do not allow - situations in which rwlock is rd-locked and there is a - pending rd-lock which is blocked (e.g. due to pending - request for wr-lock). - This is a stronger guarantee than one which is provided for - PTHREAD_RWLOCK_PREFER_READER_NP rwlocks in Linux. - MDL subsystem deadlock detector relies on this property for - its correctness. - 2) They are optimized for uncontended wr-lock/unlock case. - This is scenario in which they are most oftenly used - within MDL subsystem. Optimizing for it gives significant - performance improvements in some of tests involving many - connections. - - Another important requirement imposed on this type of rwlock - by the MDL subsystem is that it should be OK to destroy rwlock - object which is in unlocked state even though some threads might - have not yet fully left unlock operation for it (of course there - is an external guarantee that no thread will try to lock rwlock - which is destroyed). - Putting it another way the unlock operation should not access - rwlock data after changing its state to unlocked. - - TODO/FIXME: We should consider alleviating this requirement as - it blocks us from doing certain performance optimizations. -*/ - -typedef struct st_rw_pr_lock_t { - /** - Lock which protects the structure. - Also held for the duration of wr-lock. - */ - native_mutex_t lock; - /** - Condition variable which is used to wake-up - writers waiting for readers to go away. - */ - native_cond_t no_active_readers; - /** Number of active readers. */ - uint active_readers; - /** Number of writers waiting for readers to go away. */ - uint writers_waiting_readers; - /** Indicates whether there is an active writer. */ - my_bool active_writer; -#ifdef SAFE_MUTEX - /** Thread holding wr-lock (for debug purposes only). */ - my_thread_t writer_thread; -#endif -} rw_pr_lock_t; - -extern int rw_pr_init(rw_pr_lock_t *); -extern int rw_pr_rdlock(rw_pr_lock_t *); -extern int rw_pr_wrlock(rw_pr_lock_t *); -extern int rw_pr_unlock(rw_pr_lock_t *); -extern int rw_pr_destroy(rw_pr_lock_t *); - -static inline void -rw_pr_lock_assert_write_owner(const rw_pr_lock_t *rwlock MY_ATTRIBUTE((unused))) -{ -#ifdef SAFE_MUTEX - DBUG_ASSERT(rwlock->active_writer && - my_thread_equal(my_thread_self(), rwlock->writer_thread)); -#endif -} - -static inline void -rw_pr_lock_assert_not_write_owner(const rw_pr_lock_t *rwlock MY_ATTRIBUTE((unused))) -{ -#ifdef SAFE_MUTEX - DBUG_ASSERT(!rwlock->active_writer || - !my_thread_equal(my_thread_self(), rwlock->writer_thread)); -#endif -} - -C_MODE_END - -#endif /* THR_RWLOCK_INCLUDED */ |