diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/my_pthread.h | 106 | ||||
| -rw-r--r-- | include/mysql/psi/mysql_thread.h | 88 |
2 files changed, 69 insertions, 125 deletions
diff --git a/include/my_pthread.h b/include/my_pthread.h index 5cf181596ad..27ab5ba23fe 100644 --- a/include/my_pthread.h +++ b/include/my_pthread.h @@ -594,7 +594,7 @@ int my_pthread_fastmutex_lock(my_pthread_fastmutex_t *mp); /* Use our own version of read/write locks */ #define NEED_MY_RW_LOCK 1 #define rw_lock_t my_rw_lock_t -#define my_rwlock_init(A,B) my_rw_init((A), 0) +#define my_rwlock_init(A,B) my_rw_init((A)) #define rw_rdlock(A) my_rw_rdlock((A)) #define rw_wrlock(A) my_rw_wrlock((A)) #define rw_tryrdlock(A) my_rw_tryrdlock((A)) @@ -606,49 +606,82 @@ int my_pthread_fastmutex_lock(my_pthread_fastmutex_t *mp); #endif /* USE_MUTEX_INSTEAD_OF_RW_LOCKS */ -/* - Portable read-write locks which prefer readers. - - Required by some algorithms in order to provide correctness. +/** + 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. */ -#if defined(HAVE_PTHREAD_RWLOCK_RDLOCK) && defined(HAVE_PTHREAD_RWLOCKATTR_SETKIND_NP) -/* - On systems which have a way to specify that readers should - be preferred through attribute mechanism (e.g. Linux) we use - system implementation of read/write locks. -*/ -#define rw_pr_lock_t pthread_rwlock_t +typedef struct st_rw_pr_lock_t { + /** + Lock which protects the structure. + Also held for the duration of wr-lock. + */ + pthread_mutex_t lock; + /** + Condition variable which is used to wake-up + writers waiting for readers to go away. + */ + pthread_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). */ + pthread_t writer_thread; +#endif +} rw_pr_lock_t; + extern int rw_pr_init(rw_pr_lock_t *); -#define rw_pr_rdlock(A) pthread_rwlock_rdlock(A) -#define rw_pr_wrlock(A) pthread_rwlock_wrlock(A) -#define rw_pr_tryrdlock(A) pthread_rwlock_tryrdlock(A) -#define rw_pr_trywrlock(A) pthread_rwlock_trywrlock(A) -#define rw_pr_unlock(A) pthread_rwlock_unlock(A) -#define rw_pr_destroy(A) pthread_rwlock_destroy(A) +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 *); +#ifdef SAFE_MUTEX +#define rw_pr_lock_assert_write_owner(A) \ + DBUG_ASSERT((A)->active_writer && pthread_equal(pthread_self(), \ + (A)->writer_thread)) +#define rw_pr_lock_assert_not_write_owner(A) \ + DBUG_ASSERT(! (A)->active_writer || ! pthread_equal(pthread_self(), \ + (A)->writer_thread)) +#else #define rw_pr_lock_assert_write_owner(A) #define rw_pr_lock_assert_not_write_owner(A) -#else -/* Otherwise we have to use our own implementation of read/write locks. */ -#define NEED_MY_RW_LOCK 1 -struct st_my_rw_lock_t; -#define rw_pr_lock_t my_rw_lock_t -extern int rw_pr_init(struct st_my_rw_lock_t *); -#define rw_pr_rdlock(A) my_rw_rdlock((A)) -#define rw_pr_wrlock(A) my_rw_wrlock((A)) -#define rw_pr_tryrdlock(A) my_rw_tryrdlock((A)) -#define rw_pr_trywrlock(A) my_rw_trywrlock((A)) -#define rw_pr_unlock(A) my_rw_unlock((A)) -#define rw_pr_destroy(A) my_rw_destroy((A)) -#define rw_pr_lock_assert_write_owner(A) my_rw_lock_assert_write_owner((A)) -#define rw_pr_lock_assert_not_write_owner(A) my_rw_lock_assert_not_write_owner((A)) -#endif /* defined(HAVE_PTHREAD_RWLOCK_RDLOCK) && defined(HAVE_PTHREAD_RWLOCKATTR_SETKIND_NP) */ +#endif /* SAFE_MUTEX */ #ifdef NEED_MY_RW_LOCK /* - On systems which don't support native read/write locks, or don't support - read/write locks which prefer readers we have to use own implementation. + On systems which don't support native read/write locks we have + to use own implementation. */ typedef struct st_my_rw_lock_t { pthread_mutex_t lock; /* lock for structure */ @@ -656,13 +689,12 @@ typedef struct st_my_rw_lock_t { pthread_cond_t writers; /* waiting writers */ int state; /* -1:writer,0:free,>0:readers */ int waiters; /* number of waiting writers */ - my_bool prefer_readers; #ifdef SAFE_MUTEX pthread_t write_thread; #endif } my_rw_lock_t; -extern int my_rw_init(my_rw_lock_t *, my_bool *); +extern int my_rw_init(my_rw_lock_t *); extern int my_rw_destroy(my_rw_lock_t *); extern int my_rw_rdlock(my_rw_lock_t *); extern int my_rw_wrlock(my_rw_lock_t *); diff --git a/include/mysql/psi/mysql_thread.h b/include/mysql/psi/mysql_thread.h index 60b4f5d6ef4..5b8ea3dc5dc 100644 --- a/include/mysql/psi/mysql_thread.h +++ b/include/mysql/psi/mysql_thread.h @@ -141,9 +141,7 @@ typedef struct st_mysql_rwlock mysql_rwlock_t; @c mysql_prlock_t is a drop-in replacement for @c rw_pr_lock_t. @sa mysql_prlock_init @sa mysql_prlock_rdlock - @sa mysql_prlock_tryrdlock @sa mysql_prlock_wrlock - @sa mysql_prlock_trywrlock @sa mysql_prlock_unlock @sa mysql_prlock_destroy */ @@ -421,20 +419,6 @@ typedef struct st_mysql_cond mysql_cond_t; #endif /** - @def mysql_prlock_tryrdlock(RW) - Instrumented rw_pr_tryrdlock. - @c mysql_prlock_tryrdlock is a drop-in replacement - for @c rw_pr_tryrdlock. -*/ -#ifdef HAVE_PSI_INTERFACE - #define mysql_prlock_tryrdlock(RW) \ - inline_mysql_prlock_tryrdlock(RW, __FILE__, __LINE__) -#else - #define mysql_prlock_tryrdlock(RW) \ - inline_mysql_prlock_tryrdlock(RW) -#endif - -/** @def mysql_rwlock_trywrlock(RW) Instrumented rwlock_trywrlock. @c mysql_rwlock_trywrlock is a drop-in replacement @@ -449,20 +433,6 @@ typedef struct st_mysql_cond mysql_cond_t; #endif /** - @def mysql_prlock_trywrlock(RW) - Instrumented rw_pr_trywrlock. - @c mysql_prlock_trywrlock is a drop-in replacement - for @c rw_pr_trywrlock. -*/ -#ifdef HAVE_PSI_INTERFACE - #define mysql_prlock_trywrlock(RW) \ - inline_mysql_prlock_trywrlock(RW, __FILE__, __LINE__) -#else - #define mysql_prlock_trywrlock(RW) \ - inline_mysql_prlock_trywrlock(RW) -#endif - -/** @def mysql_rwlock_unlock(RW) Instrumented rwlock_unlock. @c mysql_rwlock_unlock is a drop-in replacement @@ -905,35 +875,6 @@ static inline int inline_mysql_rwlock_tryrdlock( return result; } -#ifndef DISABLE_MYSQL_PRLOCK_H -static inline int inline_mysql_prlock_tryrdlock( - mysql_prlock_t *that -#ifdef HAVE_PSI_INTERFACE - , const char *src_file, uint src_line -#endif - ) -{ - int result; -#ifdef HAVE_PSI_INTERFACE - struct PSI_rwlock_locker *locker= NULL; - PSI_rwlock_locker_state state; - if (likely(PSI_server && that->m_psi)) - { - locker= PSI_server->get_thread_rwlock_locker(&state, that->m_psi, - PSI_RWLOCK_TRYREADLOCK); - if (likely(locker != NULL)) - PSI_server->start_rwlock_rdwait(locker, src_file, src_line); - } -#endif - result= rw_pr_tryrdlock(&that->m_prlock); -#ifdef HAVE_PSI_INTERFACE - if (likely(locker != NULL)) - PSI_server->end_rwlock_rdwait(locker, result); -#endif - return result; -} -#endif - static inline int inline_mysql_rwlock_trywrlock( mysql_rwlock_t *that #ifdef HAVE_PSI_INTERFACE @@ -961,35 +902,6 @@ static inline int inline_mysql_rwlock_trywrlock( return result; } -#ifndef DISABLE_MYSQL_PRLOCK_H -static inline int inline_mysql_prlock_trywrlock( - mysql_prlock_t *that -#ifdef HAVE_PSI_INTERFACE - , const char *src_file, uint src_line -#endif - ) -{ - int result; -#ifdef HAVE_PSI_INTERFACE - struct PSI_rwlock_locker *locker= NULL; - PSI_rwlock_locker_state state; - if (likely(PSI_server && that->m_psi)) - { - locker= PSI_server->get_thread_rwlock_locker(&state, that->m_psi, - PSI_RWLOCK_TRYWRITELOCK); - if (likely(locker != NULL)) - PSI_server->start_rwlock_wrwait(locker, src_file, src_line); - } -#endif - result= rw_pr_trywrlock(&that->m_prlock); -#ifdef HAVE_PSI_INTERFACE - if (likely(locker != NULL)) - PSI_server->end_rwlock_wrwait(locker, result); -#endif - return result; -} -#endif - static inline int inline_mysql_rwlock_unlock( mysql_rwlock_t *that) { |