497 lines
12 KiB
C
497 lines
12 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
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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 copyright[] =
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"@(#) Copyright (c) 1997\n\
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Sleepycat Software Inc. All rights reserved.\n";
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static const char sccsid[] = "@(#)lock_deadlock.c 10.20 (Sleepycat) 8/21/97";
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#endif
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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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#include <stdlib.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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} locker_info;
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static int __dd_abort __P((DB_ENV *, locker_info *));
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static int __dd_build __P((DB_ENV *, u_int32_t **, int *, locker_info **));
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#ifdef DEBUG
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static void __dd_debug __P((DB_ENV *, locker_info *, u_int32_t *, int));
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#endif
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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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int
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lock_detect(lt, flags, atype)
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DB_LOCKTAB *lt;
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int flags;
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u_int32_t 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, killid;
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int do_pass, i, nlockers, nentries, ret;
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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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do_pass = 1;
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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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}
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if (!do_pass)
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return (0);
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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 DEBUG
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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 %s",
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"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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* We know that this is less than nlockers, so
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* the cast below is valid.
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*/
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killid =
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(u_int32_t)((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 %s",
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"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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free(bitmap);
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free(idmap);
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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;
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int *nlockers;
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locker_info **idmap;
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{
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DB_LOCKTAB *lt;
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DB_LOCKOBJ *op, *lockerp;
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struct __db_lock *lp;
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u_int32_t *bitmap, count, *entryp, i, id, nentries, *tmpmap;
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locker_info *id_array;
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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 ((bitmap = (u_int32_t *)calloc((size_t)count,
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sizeof(u_int32_t) * nentries)) == NULL) {
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__db_err(dbenv, "%s", strerror(ENOMEM));
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return (ENOMEM);
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}
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if ((tmpmap =
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(u_int32_t *)calloc(sizeof(u_int32_t), nentries)) == NULL) {
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__db_err(dbenv, "%s", strerror(ENOMEM));
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free(bitmap);
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return (ENOMEM);
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}
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if ((id_array = (locker_info *)calloc((size_t)count,
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sizeof(locker_info))) == NULL) {
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__db_err(dbenv, "%s", strerror(ENOMEM));
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free(bitmap);
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free(tmpmap);
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return (ENOMEM);
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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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free(bitmap);
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free(tmpmap);
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free(id_array);
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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 ((errno = __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 ((ret = __lock_getobj(lt,
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lp->holder, NULL, DB_LOCK_LOCKER, &lockerp))
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!= 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 ((ret = __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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}
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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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free(tmpmap);
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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;
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locker_info *idmap;
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u_int32_t nlockers;
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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
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* on which that 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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DB_LOCKTAB *lt;
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DB_LOCKOBJ *lockerp, *sh_obj;
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struct __db_lock *lockp;
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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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if (LOCK_TO_OFFSET(lt, lockp) != info->last_lock ||
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lockp == NULL || 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->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 DEBUG
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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;
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int nlockers;
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{
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u_int32_t *mymap;
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int i, j, nentries;
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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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/*
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* Alloc space to print 10 bytes per item waited on.
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*/
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if ((msgbuf = (char *)malloc((nlockers + 1) * 10 + 64)) == NULL) {
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errno = ENOMEM;
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__db_err(dbenv, "%s", strerror(errno));
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return;
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}
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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, "%lx\t\t", (u_long)idmap[i].id);/* Waiter. */
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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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free(msgbuf);
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}
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#endif
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