name : waiting_threads.h /* Copyright (C) 2008 MySQL AB, 2008-2009 Sun Microsystems, Inc. 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 Street, Fifth Floor, Boston, MA 02110-1335 USA */ #ifndef _waiting_threads_h #define _waiting_threads_h #include <my_sys.h> #include <lf.h> C_MODE_START typedef struct st_wt_resource_id WT_RESOURCE_ID; typedef struct st_wt_resource WT_RESOURCE; typedef struct st_wt_resource_type { my_bool (*compare)(const void *a, const void *b); const void *(*make_key)(const WT_RESOURCE_ID *id, uint *len); /* not used */ } WT_RESOURCE_TYPE; struct st_wt_resource_id { ulonglong value; const WT_RESOURCE_TYPE *type; }; /* the below differs from sizeof(WT_RESOURCE_ID) by the amount of padding */ #define sizeof_WT_RESOURCE_ID (sizeof(ulonglong)+sizeof(void*)) #define WT_WAIT_STATS 24 #define WT_CYCLE_STATS 32 extern ulonglong wt_wait_table[WT_WAIT_STATS]; extern uint32 wt_wait_stats[WT_WAIT_STATS+1]; extern uint32 wt_cycle_stats[2][WT_CYCLE_STATS+1]; extern uint32 wt_success_stats; typedef struct st_wt_thd { /* XXX there's no protection (mutex) against concurrent access of the dynarray below. it is assumed that a caller will have it anyway (not to protect this array but to protect its own - caller's - data structures), and we'll get it for free. A caller needs to ensure that a blocker won't release a resource before a blocked thread starts waiting, which is usually done with a mutex. If the above assumption is wrong, we'll need to add a mutex here. */ DYNAMIC_ARRAY my_resources; /* 'waiting_for' is modified under waiting_for->lock, and only by thd itself 'waiting_for' is read lock-free (using pinning protocol), but a thd object can read its own 'waiting_for' without any locks or tricks. */ WT_RESOURCE *waiting_for; LF_PINS *pins; /* pointers to values */ const ulong *timeout_short; const ulong *deadlock_search_depth_short; const ulong *timeout_long; const ulong *deadlock_search_depth_long; /* weight relates to the desirability of a transaction being killed if it's part of a deadlock. In a deadlock situation transactions with lower weights are killed first. Examples of using the weight to implement different selection strategies: 1. Latest Keep all weights equal. 2. Random Assign weights at random. (variant: modify a weight randomly before every lock request) 3. Youngest Set weight to -NOW() 4. Minimum locks count locks granted in your lock manager, store the value as a weight 5. Minimum work depends on the definition of "work". For example, store the number of rows modifies in this transaction (or a length of REDO log for a transaction) as a weight. It is only statistically relevant and is not protected by any locks. */ ulong volatile weight; /* 'killed' is indirectly protected by waiting_for->lock because a killed thread needs to clear its 'waiting_for' and thus needs a lock. That is a thread needs an exclusive lock to read 'killed' reliably. But other threads may change 'killed' from 0 to 1, a shared lock is enough for that. */ my_bool killed; #ifndef DBUG_OFF const char *name; #endif } WT_THD; #define WT_TIMEOUT ETIMEDOUT #define WT_OK 0 #define WT_DEADLOCK -1 #define WT_DEPTH_EXCEEDED -2 #define WT_FREE_TO_GO -3 void wt_init(void); void wt_end(void); void wt_thd_lazy_init(WT_THD *, const ulong *, const ulong *, const ulong *, const ulong *); void wt_thd_destroy(WT_THD *); int wt_thd_will_wait_for(WT_THD *, WT_THD *, const WT_RESOURCE_ID *); int wt_thd_cond_timedwait(WT_THD *, mysql_mutex_t *); void wt_thd_release(WT_THD *, const WT_RESOURCE_ID *); #define wt_thd_release_all(THD) wt_thd_release((THD), 0) my_bool wt_resource_id_memcmp(const void *, const void *); C_MODE_END #endif