From 9474c1a0b62cad57b62855d09a201670385caa80 Mon Sep 17 00:00:00 2001 From: Howard Chu Date: Mon, 1 Jul 2013 13:41:23 -0700 Subject: [PATCH] ITS#7635 fix read txn potential data race --- libraries/liblmdb/mdb.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c index 40b46e8..84405e8 100644 --- a/libraries/liblmdb/mdb.c +++ b/libraries/liblmdb/mdb.c @@ -1743,6 +1743,7 @@ mdb_txn_renew0(MDB_txn *txn) unsigned int i; uint16_t x; int rc, new_notls = 0; + pgno_t lastpg2; /* Setup db info */ txn->mt_numdbs = env->me_numdbs; @@ -1811,6 +1812,17 @@ mdb_txn_renew0(MDB_txn *txn) /* Copy the DB info and flags */ memcpy(txn->mt_dbs, env->me_metas[txn->mt_toggle]->mm_dbs, 2 * sizeof(MDB_db)); + /* In a read txn, there is a data race here. Make sure our + * last_pg/next_pg are up to date. + */ + lastpg2 = env->me_metas[txn->mt_toggle]->mm_last_pg+1; + if (lastpg2 != txn->mt_next_pgno) { + txn->mt_next_pgno = lastpg2; + /* When this situation occurs, the txnid will certainly also + * be out of date. But as noted before, we don't care about having + * up to date read txn IDs. + */ + } for (i=2; imt_numdbs; i++) { x = env->me_dbflags[i]; txn->mt_dbs[i].md_flags = x & PERSISTENT_FLAGS;