503 lines
13 KiB
C
503 lines
13 KiB
C
/*-
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* See the file LICENSE for redistribution information.
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*
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* Copyright (c) 1996, 1997, 1998
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* Sleepycat Software. All rights reserved.
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*/
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#include "config.h"
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#ifndef lint
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static const char sccsid[] = "@(#)lock_deadlock.c 10.37 (Sleepycat) 10/4/98";
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#endif /* not lint */
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#ifndef NO_SYSTEM_INCLUDES
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#include <sys/types.h>
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#include <errno.h>
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#include <string.h>
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#endif
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#include "db_int.h"
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#include "shqueue.h"
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#include "db_shash.h"
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#include "lock.h"
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#include "common_ext.h"
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#define ISSET_MAP(M, N) (M[(N) / 32] & (1 << (N) % 32))
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#define CLEAR_MAP(M, N) { \
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u_int32_t __i; \
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for (__i = 0; __i < (N); __i++) \
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M[__i] = 0; \
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}
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#define SET_MAP(M, B) (M[(B) / 32] |= (1 << ((B) % 32)))
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#define CLR_MAP(M, B) (M[(B) / 32] &= ~(1 << ((B) % 32)))
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#define OR_MAP(D, S, N) { \
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u_int32_t __i; \
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for (__i = 0; __i < (N); __i++) \
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D[__i] |= S[__i]; \
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}
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#define BAD_KILLID 0xffffffff
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typedef struct {
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int valid;
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u_int32_t id;
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DB_LOCK last_lock;
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db_pgno_t pgno;
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} locker_info;
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static int __dd_abort __P((DB_ENV *, locker_info *));
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static int __dd_build
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__P((DB_ENV *, u_int32_t **, u_int32_t *, locker_info **));
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static u_int32_t
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*__dd_find __P((u_int32_t *, locker_info *, u_int32_t));
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#ifdef DIAGNOSTIC
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static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, u_int32_t));
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#endif
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int
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lock_detect(lt, flags, atype)
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DB_LOCKTAB *lt;
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u_int32_t flags, atype;
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{
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DB_ENV *dbenv;
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locker_info *idmap;
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u_int32_t *bitmap, *deadlock, i, killid, nentries, nlockers;
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int do_pass, ret;
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LOCK_PANIC_CHECK(lt);
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/* Validate arguments. */
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if ((ret =
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__db_fchk(lt->dbenv, "lock_detect", flags, DB_LOCK_CONFLICT)) != 0)
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return (ret);
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/* Check if a detector run is necessary. */
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dbenv = lt->dbenv;
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if (LF_ISSET(DB_LOCK_CONFLICT)) {
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/* Make a pass every time a lock waits. */
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LOCK_LOCKREGION(lt);
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do_pass = dbenv->lk_info->region->need_dd != 0;
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UNLOCK_LOCKREGION(lt);
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if (!do_pass)
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return (0);
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}
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/* Build the waits-for bitmap. */
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if ((ret = __dd_build(dbenv, &bitmap, &nlockers, &idmap)) != 0)
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return (ret);
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if (nlockers == 0)
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return (0);
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#ifdef DIAGNOSTIC
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if (dbenv->db_verbose != 0)
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__dd_debug(dbenv, idmap, bitmap, nlockers);
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#endif
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/* Find a deadlock. */
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deadlock = __dd_find(bitmap, idmap, nlockers);
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nentries = ALIGN(nlockers, 32) / 32;
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killid = BAD_KILLID;
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if (deadlock != NULL) {
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/* Kill someone. */
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switch (atype) {
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case DB_LOCK_OLDEST:
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/*
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* Find the first bit set in the current
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* array and then look for a lower tid in
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* the array.
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*/
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for (i = 0; i < nlockers; i++)
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if (ISSET_MAP(deadlock, i))
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killid = i;
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if (killid == BAD_KILLID) {
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__db_err(dbenv,
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"warning: could not find locker to abort");
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break;
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}
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/*
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* The oldest transaction has the lowest
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* transaction id.
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*/
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for (i = killid + 1; i < nlockers; i++)
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if (ISSET_MAP(deadlock, i) &&
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idmap[i].id < idmap[killid].id)
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killid = i;
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break;
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case DB_LOCK_DEFAULT:
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case DB_LOCK_RANDOM:
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/*
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* We are trying to calculate the id of the
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* locker whose entry is indicated by deadlock.
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*/
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killid = (deadlock - bitmap) / nentries;
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break;
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case DB_LOCK_YOUNGEST:
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/*
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* Find the first bit set in the current
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* array and then look for a lower tid in
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* the array.
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*/
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for (i = 0; i < nlockers; i++)
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if (ISSET_MAP(deadlock, i))
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killid = i;
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if (killid == BAD_KILLID) {
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__db_err(dbenv,
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"warning: could not find locker to abort");
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break;
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}
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/*
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* The youngest transaction has the highest
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* transaction id.
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*/
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for (i = killid + 1; i < nlockers; i++)
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if (ISSET_MAP(deadlock, i) &&
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idmap[i].id > idmap[killid].id)
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killid = i;
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break;
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default:
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killid = BAD_KILLID;
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ret = EINVAL;
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}
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/* Kill the locker with lockid idmap[killid]. */
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if (dbenv->db_verbose != 0 && killid != BAD_KILLID)
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__db_err(dbenv, "Aborting locker %lx",
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(u_long)idmap[killid].id);
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if (killid != BAD_KILLID &&
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(ret = __dd_abort(dbenv, &idmap[killid])) != 0)
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__db_err(dbenv,
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"warning: unable to abort locker %lx",
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(u_long)idmap[killid].id);
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}
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__os_free(bitmap, 0);
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__os_free(idmap, 0);
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return (ret);
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}
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/*
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* ========================================================================
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* Utilities
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*/
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static int
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__dd_build(dbenv, bmp, nlockers, idmap)
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DB_ENV *dbenv;
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u_int32_t **bmp, *nlockers;
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locker_info **idmap;
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{
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struct __db_lock *lp;
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DB_LOCKTAB *lt;
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DB_LOCKOBJ *op, *lo, *lockerp;
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u_int8_t *pptr;
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locker_info *id_array;
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u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap;
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int is_first, ret;
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lt = dbenv->lk_info;
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/*
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* We'll check how many lockers there are, add a few more in for
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* good measure and then allocate all the structures. Then we'll
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* verify that we have enough room when we go back in and get the
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* mutex the second time.
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*/
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LOCK_LOCKREGION(lt);
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retry: count = lt->region->nlockers;
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lt->region->need_dd = 0;
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UNLOCK_LOCKREGION(lt);
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if (count == 0) {
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*nlockers = 0;
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return (0);
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}
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if (dbenv->db_verbose)
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__db_err(dbenv, "%lu lockers", (u_long)count);
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count += 10;
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nentries = ALIGN(count, 32) / 32;
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/*
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* Allocate enough space for a count by count bitmap matrix.
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*
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* XXX
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* We can probably save the malloc's between iterations just
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* reallocing if necessary because count grew by too much.
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*/
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if ((ret = __os_calloc((size_t)count,
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sizeof(u_int32_t) * nentries, &bitmap)) != 0)
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return (ret);
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if ((ret = __os_calloc(sizeof(u_int32_t), nentries, &tmpmap)) != 0) {
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__os_free(bitmap, sizeof(u_int32_t) * nentries);
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return (ret);
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}
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if ((ret =
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__os_calloc((size_t)count, sizeof(locker_info), &id_array)) != 0) {
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__os_free(bitmap, count * sizeof(u_int32_t) * nentries);
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__os_free(tmpmap, sizeof(u_int32_t) * nentries);
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return (ret);
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}
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/*
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* Now go back in and actually fill in the matrix.
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*/
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LOCK_LOCKREGION(lt);
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if (lt->region->nlockers > count) {
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__os_free(bitmap, count * sizeof(u_int32_t) * nentries);
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__os_free(tmpmap, sizeof(u_int32_t) * nentries);
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__os_free(id_array, count * sizeof(locker_info));
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goto retry;
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}
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/*
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* First we go through and assign each locker a deadlock detector id.
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* Note that we fill in the idmap in the next loop since that's the
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* only place where we conveniently have both the deadlock id and the
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* actual locker.
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*/
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for (id = 0, i = 0; i < lt->region->table_size; i++)
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for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj);
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op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj))
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if (op->type == DB_LOCK_LOCKER)
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op->dd_id = id++;
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/*
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* We go through the hash table and find each object. For each object,
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* we traverse the waiters list and add an entry in the waitsfor matrix
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* for each waiter/holder combination.
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*/
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for (i = 0; i < lt->region->table_size; i++) {
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for (op = SH_TAILQ_FIRST(<->hashtab[i], __db_lockobj);
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op != NULL; op = SH_TAILQ_NEXT(op, links, __db_lockobj)) {
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if (op->type != DB_LOCK_OBJTYPE)
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continue;
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CLEAR_MAP(tmpmap, nentries);
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/*
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* First we go through and create a bit map that
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* represents all the holders of this object.
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*/
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for (lp = SH_TAILQ_FIRST(&op->holders, __db_lock);
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lp != NULL;
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lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
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if (__lock_getobj(lt, lp->holder,
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NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
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__db_err(dbenv,
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"warning unable to find object");
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continue;
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}
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id_array[lockerp->dd_id].id = lp->holder;
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id_array[lockerp->dd_id].valid = 1;
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/*
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* If the holder has already been aborted, then
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* we should ignore it for now.
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*/
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if (lp->status == DB_LSTAT_HELD)
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SET_MAP(tmpmap, lockerp->dd_id);
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}
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/*
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* Next, for each waiter, we set its row in the matrix
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* equal to the map of holders we set up above.
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*/
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for (is_first = 1,
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lp = SH_TAILQ_FIRST(&op->waiters, __db_lock);
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lp != NULL;
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is_first = 0,
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lp = SH_TAILQ_NEXT(lp, links, __db_lock)) {
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if (__lock_getobj(lt, lp->holder,
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NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
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__db_err(dbenv,
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"warning unable to find object");
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continue;
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}
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id_array[lockerp->dd_id].id = lp->holder;
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id_array[lockerp->dd_id].valid = 1;
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/*
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* If the transaction is pending abortion, then
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* ignore it on this iteration.
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*/
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if (lp->status != DB_LSTAT_WAITING)
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continue;
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entryp = bitmap + (nentries * lockerp->dd_id);
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OR_MAP(entryp, tmpmap, nentries);
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/*
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* If this is the first waiter on the queue,
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* then we remove the waitsfor relationship
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* with oneself. However, if it's anywhere
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* else on the queue, then we have to keep
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* it and we have an automatic deadlock.
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*/
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if (is_first)
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CLR_MAP(entryp, lockerp->dd_id);
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}
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}
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}
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/* Now for each locker; record its last lock. */
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for (id = 0; id < count; id++) {
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if (!id_array[id].valid)
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continue;
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if (__lock_getobj(lt,
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id_array[id].id, NULL, DB_LOCK_LOCKER, &lockerp) != 0) {
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__db_err(dbenv,
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"No locks for locker %lu", (u_long)id_array[id].id);
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continue;
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}
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lp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
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if (lp != NULL) {
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id_array[id].last_lock = LOCK_TO_OFFSET(lt, lp);
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lo = (DB_LOCKOBJ *)((u_int8_t *)lp + lp->obj);
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pptr = SH_DBT_PTR(&lo->lockobj);
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if (lo->lockobj.size >= sizeof(db_pgno_t))
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memcpy(&id_array[id].pgno, pptr,
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sizeof(db_pgno_t));
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else
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id_array[id].pgno = 0;
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}
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}
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/* Pass complete, reset the deadlock detector bit. */
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lt->region->need_dd = 0;
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UNLOCK_LOCKREGION(lt);
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/*
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* Now we can release everything except the bitmap matrix that we
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* created.
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*/
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*nlockers = id;
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*idmap = id_array;
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*bmp = bitmap;
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__os_free(tmpmap, sizeof(u_int32_t) * nentries);
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return (0);
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}
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static u_int32_t *
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__dd_find(bmp, idmap, nlockers)
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u_int32_t *bmp, nlockers;
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locker_info *idmap;
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{
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u_int32_t i, j, nentries, *mymap, *tmpmap;
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/*
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* For each locker, OR in the bits from the lockers on which that
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* locker is waiting.
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*/
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nentries = ALIGN(nlockers, 32) / 32;
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for (mymap = bmp, i = 0; i < nlockers; i++, mymap += nentries) {
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if (!idmap[i].valid)
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continue;
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for (j = 0; j < nlockers; j++) {
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if (ISSET_MAP(mymap, j)) {
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/* Find the map for this bit. */
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tmpmap = bmp + (nentries * j);
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OR_MAP(mymap, tmpmap, nentries);
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if (ISSET_MAP(mymap, i))
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return (mymap);
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}
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}
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}
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return (NULL);
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}
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static int
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__dd_abort(dbenv, info)
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DB_ENV *dbenv;
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locker_info *info;
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{
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struct __db_lock *lockp;
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DB_LOCKTAB *lt;
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DB_LOCKOBJ *lockerp, *sh_obj;
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int ret;
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lt = dbenv->lk_info;
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LOCK_LOCKREGION(lt);
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/* Find the locker's last lock. */
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if ((ret =
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__lock_getobj(lt, info->id, NULL, DB_LOCK_LOCKER, &lockerp)) != 0)
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goto out;
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lockp = SH_LIST_FIRST(&lockerp->heldby, __db_lock);
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/*
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* It's possible that this locker was already aborted.
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* If that's the case, make sure that we remove its
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* locker from the hash table.
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*/
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if (lockp == NULL) {
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HASHREMOVE_EL(lt->hashtab, __db_lockobj,
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links, lockerp, lt->region->table_size, __lock_lhash);
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SH_TAILQ_INSERT_HEAD(<->region->free_objs,
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lockerp, links, __db_lockobj);
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lt->region->nlockers--;
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goto out;
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} else if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock ||
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lockp->status != DB_LSTAT_WAITING)
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goto out;
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/* Abort lock, take it off list, and wake up this lock. */
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lockp->status = DB_LSTAT_ABORTED;
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lt->region->ndeadlocks++;
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SH_LIST_REMOVE(lockp, locker_links, __db_lock);
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sh_obj = (DB_LOCKOBJ *)((u_int8_t *)lockp + lockp->obj);
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SH_TAILQ_REMOVE(&sh_obj->waiters, lockp, links, __db_lock);
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(void)__db_mutex_unlock(&lockp->mutex, lt->reginfo.fd);
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ret = 0;
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out: UNLOCK_LOCKREGION(lt);
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return (ret);
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}
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#ifdef DIAGNOSTIC
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static void
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__dd_debug(dbenv, idmap, bitmap, nlockers)
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DB_ENV *dbenv;
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locker_info *idmap;
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u_int32_t *bitmap, nlockers;
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{
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u_int32_t i, j, *mymap, nentries;
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int ret;
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char *msgbuf;
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__db_err(dbenv, "Waitsfor array");
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__db_err(dbenv, "waiter\twaiting on");
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/* Allocate space to print 10 bytes per item waited on. */
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#undef MSGBUF_LEN
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#define MSGBUF_LEN ((nlockers + 1) * 10 + 64)
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if ((ret = __os_malloc(MSGBUF_LEN, NULL, &msgbuf)) != 0)
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return;
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nentries = ALIGN(nlockers, 32) / 32;
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for (mymap = bitmap, i = 0; i < nlockers; i++, mymap += nentries) {
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if (!idmap[i].valid)
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continue;
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sprintf(msgbuf, /* Waiter. */
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"%lx/%lu:\t", (u_long)idmap[i].id, (u_long)idmap[i].pgno);
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for (j = 0; j < nlockers; j++)
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if (ISSET_MAP(mymap, j))
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sprintf(msgbuf, "%s %lx", msgbuf,
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(u_long)idmap[j].id);
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(void)sprintf(msgbuf,
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"%s %lu", msgbuf, (u_long)idmap[i].last_lock);
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__db_err(dbenv, msgbuf);
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}
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__os_free(msgbuf, MSGBUF_LEN);
|
|
}
|
|
#endif
|