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ITS#7635 fix read txn potential data race

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This commit is contained in:
Howard Chu 2013-07-01 13:41:23 -07:00
parent 3347a02905
commit 9474c1a0b6
1 changed files with 12 additions and 0 deletions
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12
libraries/liblmdb/mdb.c
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@ -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* be out of date.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; i<txn->mt_numdbs; i++) {
x = env->me_dbflags[i];
txn->mt_dbs[i].md_flags = x & PERSISTENT_FLAGS;