lock.h

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/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998, 1999, 2000
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: lock_8h-source.html,v 1.1 2008/06/08 10:19:54 sebdiaz Exp $
 */

#ifndef DB_LOCK_DEFAULT_N
#define DB_LOCK_DEFAULT_N       1000    /* Default # of locks in region. */
#endif

/*
 * Out of band value for a lock.  Locks contain an offset into a lock region,
 * so we use an invalid region offset to indicate an invalid or unset lock.
 */
#define LOCK_INVALID    INVALID_ROFF

/*
 * The locker id space is divided between the transaction manager and the lock
 * manager.  Lock IDs start at 0 and go to DB_LOCK_MAXID.  Txn IDs start at
 * DB_LOCK_MAXID + 1 and go up to TXN_INVALID.
 */
#define DB_LOCK_MAXID           0x7fffffff

/*
 * DB_LOCKREGION --
 *      The lock shared region.
 */
typedef struct __db_lockregion {
        u_int32_t       id;             /* unique id generator */
        u_int32_t       need_dd;        /* flag for deadlock detector */
        u_int32_t       detect;         /* run dd on every conflict */
                                        /* free lock header */
        SH_TAILQ_HEAD(__flock) free_locks;
                                        /* free obj header */
        SH_TAILQ_HEAD(__fobj) free_objs;
                                        /* free locker header */
        SH_TAILQ_HEAD(__flocker) free_lockers;
        SH_TAILQ_HEAD(__dobj) dd_objs;  /* objects with waiters */
        u_int32_t       maxlocks;       /* maximum number of locks in table */
        u_int32_t       table_size;     /* size of hash table */
        u_int32_t       nmodes;         /* number of lock modes */
        u_int32_t       nlockers;       /* number of lockers */
        u_int32_t       maxnlockers;    /* maximum number of lockers */
        roff_t          conf_off;       /* offset of conflicts array */
        roff_t          obj_off;        /* offset of object hash table */
        roff_t          osynch_off;     /* offset of the object mutex table */
        roff_t          locker_off;     /* offset of locker hash table */
        roff_t          lsynch_off;     /* offset of the locker mutex table */
        u_int32_t       nconflicts;     /* number of lock conflicts */
        u_int32_t       nrequests;      /* number of lock gets */
        u_int32_t       nreleases;      /* number of lock puts */
        u_int32_t       nnowaits;       /* number of lock requests that would
                                           have waited without nowait */
        u_int32_t       ndeadlocks;     /* number of deadlocks */
} DB_LOCKREGION;

/*
 * Since we will store DBTs in shared memory, we need the equivalent of a
 * DBT that will work in shared memory.
 */
typedef struct __sh_dbt {
        u_int32_t size;                 /* Byte length. */
        ssize_t   off;                  /* Region offset. */
} SH_DBT;

#define SH_DBT_PTR(p)   ((void *)(((u_int8_t *)(p)) + (p)->off))

/*
 * Object structures;  these live in the object hash table.
 */
typedef struct __db_lockobj {
        SH_DBT  lockobj;                /* Identifies object locked. */
        SH_TAILQ_ENTRY links;           /* Links for free list or hash list. */
        SH_TAILQ_ENTRY dd_links;        /* Links for dd list. */
        SH_TAILQ_HEAD(__wait) waiters;  /* List of waiting locks. */
        SH_TAILQ_HEAD(__hold) holders;  /* List of held locks. */
                                        /* Declare room in the object to hold
                                         * typical DB lock structures so that
                                         * we do not have to allocate them from
                                         * shalloc at run-time. */
        u_int8_t objdata[sizeof(struct __db_ilock)];
} DB_LOCKOBJ;

/*
 * Locker structures; these live in the locker hash table.
 */
typedef struct __db_locker {
        u_int32_t id;                   /* Locker id. */
        u_int32_t dd_id;                /* Deadlock detector id. */
        size_t master_locker;           /* Locker of master transaction. */
        size_t parent_locker;           /* Parent of this child. */
        SH_LIST_HEAD(_child) child_locker;      /* List of descendant txns;
                                                   only used in a "master"
                                                   txn. */
        SH_LIST_ENTRY child_link;       /* Links transactions in the family;
                                           elements of the child_locker
                                           list. */
        SH_TAILQ_ENTRY links;           /* Links for free list. */
        SH_LIST_HEAD(_held) heldby;     /* Locks held by this locker. */

#define DB_LOCKER_DELETED       0x0001
        u_int32_t flags;
} DB_LOCKER;

/*
 * Lockers can be freed if they are not part of a transaction family.
 * Members of a family either point at the master transaction or are
 * the master transaction and have children lockers.
 */
#define LOCKER_FREEABLE(lp)                                             \
    ((lp)->master_locker == TXN_INVALID_ID &&                           \
    SH_LIST_FIRST(&(lp)->child_locker, __db_locker) == NULL)

/*
 * DB_LOCKTAB --
 *      The primary library lock data structure (i.e., the one referenced
 * by the environment, as opposed to the internal one laid out in the region.)
 */
typedef struct __db_locktab {
        DB_ENV          *dbenv;         /* Environment. */
        REGINFO          reginfo;       /* Region information. */
        u_int8_t        *conflicts;     /* Pointer to conflict matrix. */
        DB_HASHTAB      *obj_tab;       /* Beginning of object hash table. */
        DB_HASHTAB      *locker_tab;    /* Beginning of locker hash table. */
} DB_LOCKTAB;

/* Test for conflicts. */
#define CONFLICTS(T, R, HELD, WANTED) \
        (T)->conflicts[(HELD) * (R)->nmodes + (WANTED)]

#define OBJ_LINKS_VALID(L) ((L)->links.stqe_prev != -1)

struct __db_lock {
        /*
         * Wait on mutex to wait on lock.  You reference your own mutex with
         * ID 0 and others reference your mutex with ID 1.
         */
        MUTEX           mutex;

        u_int32_t       holder;         /* Who holds this lock. */
        u_int32_t       gen;            /* Generation count. */
        SH_TAILQ_ENTRY  links;          /* Free or holder/waiter list. */
        SH_LIST_ENTRY   locker_links;   /* List of locks held by a locker. */
        u_int32_t       refcount;       /* Reference count the lock. */
        db_lockmode_t   mode;           /* What sort of lock. */
        ssize_t         obj;            /* Relative offset of object struct. */
        db_status_t     status;         /* Status of this lock. */
};

/*
 * Flag values for __lock_put_internal:
 * DB_LOCK_DOALL:     Unlock all references in this lock (instead of only 1).
 * DB_LOCK_FREE:      Free the lock (used in checklocker).
 * DB_LOCK_IGNOREDEL: Remove from the locker hash table even if already
                      deleted (used in checklocker).
 * DB_LOCK_NOPROMOTE: Don't bother running promotion when releasing locks
 *                    (used by __lock_put_internal).
 * DB_LOCK_UNLINK:    Remove from the locker links (used in checklocker).
 */
#define DB_LOCK_DOALL           0x001
#define DB_LOCK_FREE            0x002
#define DB_LOCK_IGNOREDEL       0x004
#define DB_LOCK_NOPROMOTE       0x008
#define DB_LOCK_UNLINK          0x010

/*
 * Macros to get/release different types of mutexes.
 */
#define OBJECT_LOOKUP(lt, ndx, dbt, sh_obj)                             \
        HASHLOOKUP((lt)->objtab,                                        \
            ndx, __db_lockobj, links, dbt, sh_obj, CDB___lock_cmp);

#define OBJECT_LOCK(lt, reg, obj, ndx)                                  \
        ndx = CDB___lock_ohash(obj) % (reg)->table_size
#define SHOBJECT_LOCK(lt, reg, shobj, ndx)                              \
        ndx = CDB___lock_lhash(shobj) % (reg)->table_size
#define OBJECT_UNLOCK(lt, ndx)

#define LOCKER_LOOKUP(lt, ndx, locker, sh_locker)                       \
        HASHLOOKUP((lt)->lockertab,                                     \
            ndx, __db_locker, links, locker, sh_locker, CDB___lock_locker_cmp);

#define LOCKREGION(dbenv, lt)  R_LOCK((dbenv), &(lt)->reginfo)
#define UNLOCKREGION(dbenv, lt)  R_UNLOCK((dbenv), &(lt)->reginfo)
#include "lock_ext.h"

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