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