From 8230b1b63003f5e4910948687c0ceba0bed1d624 Mon Sep 17 00:00:00 2001 From: "leo@yuriev.ru" Date: Fri, 17 Oct 2014 22:35:41 +0000 Subject: [PATCH] ITS#7970 LMDB: Critical Heisenbug Inconsistent reading & SIGSEGV due to the race condition. --- libraries/liblmdb/mdb.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c index 89d4a2a..27dbb9b 100644 --- a/libraries/liblmdb/mdb.c +++ b/libraries/liblmdb/mdb.c @@ -2539,7 +2539,10 @@ mdb_txn_renew0(MDB_txn *txn) return rc; } } - txn->mt_txnid = r->mr_txnid = ti->mti_txnid; + do /* LY: Retry on a race, ITS#7970. */ + r->mr_txnid = ti->mti_txnid; + while(r->mr_txnid != ti->mti_txnid); + txn->mt_txnid = r->mr_txnid; txn->mt_u.reader = r; meta = env->me_metas[txn->mt_txnid & 1]; }