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/* 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
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