Infinite loop at db_open

Question

Hi!
There is another problem on multi-process env.
$ pstack 17778
#0 0x0057cc62 in memcmp () from /lib/tls/libc.so.6
#1 0x088652e0 in ?? ()
#2 0x08291bf6 in __env_setup ()
#3 0x081ad39e in __db_open ()
#4 0x082a5639 in __db_open_pp ()
#5 0x0814dc2c in btreeCreateDataTable ()
#6 0x0814e21a in sqlite3BtreeCursor ()
#7 0x08152a56 in btreeLockSchema ()
#8 0x08152be9 in sqlite3BtreeLockTable ()
#9 0x0816c0d7 in sqlite3VdbeExec ()
#10 0x0815fd06 in sqlite3Step ()
#11 0x0815ff06 in sqlite3_step ()
#12 0x08189a39 in sqlite3_exec ()
#13 0x0818db72 in sqlite3InitOne ()
#14 0x0818dd16 in sqlite3Init ()
#15 0x0818de26 in sqlite3ReadSchema ()
#16 0x0817a7fa in sqlite3LocateTable ()
#17 0x0819442b in selectExpander ()
#18 0x0816e112 in sqlite3WalkSelect ()
#19 0x08194b2d in sqlite3SelectExpand ()
#20 0x08194cd1 in sqlite3SelectPrep ()
#21 0x081952cd in sqlite3Select ()
#22 0x081a476a in yy_reduce ()
#23 0x081a6839 in sqlite3Parser ()
#24 0x081a74f3 in sqlite3RunParser ()
#25 0x0818e2be in sqlite3Prepare ()
#26 0x0818e660 in sqlite3LockAndPrepare ()
#27 0x0818e84d in sqlite3_prepare ()
#28 0x081899d2 in sqlite3_exec ()
#29 0x08196d37 in sqlite3_get_table ()
#30 0x08063d2c in _db_open_ex ()
#31 0x080637a8 in _db_open ()
...On multi-process env, somecase, env->dblist is crashed.
   馹../src/db/db.c葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺衆
   477 TAILQ_FOREACH(ldbp, &env->dblist, dblistlinks) {
   478 /*
   479 * There are three cases: on-disk database (first c
   480 * named in-memory database (second clause), tempor
   481 * (never matches; no clause).
   482 */
   483 if (!F_ISSET(dbp, DB_AM_INMEM)) {
  >484 if (memcmp(ldbp->fileid, dbp->fileid, DB_FI
   485 == 0 && ldbp->meta_pgno == dbp->meta_pg
   486 break;
   487 } else if (dname != NULL) {
   488 if (F_ISSET(ldbp, DB_AM_INMEM) &&
   489 ldbp->dname != NULL &&
   章葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺葺
multi-thre process 17778 In: __env_setup Line: 484 PC: 0x8291bf6
    at ../src/db/db.c:484
(gdb) p env->dblist
$1 = {tqh_first = 0x888a268, tqh_last = 0x88273ac}
(gdb) p ldbp->dblistlinks
$2 = {tqe_next = 0x888a268, tqe_prev = 0x888a344}
(gdb) p ldbp->dblistlinks .tqe_next->dblistlinks
$3 = {tqe_next = 0x888a268, tqe_prev = 0x888a344} So, I just add defense codes.
src/db/db.c
@@ -475,6 +475,13 @@
        MUTEX_LOCK(env, env->mtx_dblist);
        maxid = 0;
        TAILQ_FOREACH(ldbp, &env->dblist, dblistlinks) {
+               /* infinite loop fix */
+               if (ldbp != env->dblist.tqh_last &&
+                   ldbp == ldbp->dblistlinks.tqe_next) {
+                       MUTEX_UNLOCK(env, env->mtx_dblist);
+                       return (-1);
+               }
+Is it ok?
I want to know why env->dblist is crashed.
Thanks.

Answer 1

Hello,
Is it possible to provide a test case which illustrates this scenario?
Thank you,
Sandra