From 9bd6b9d9f6591d3f5138c2a831340a88a5e4de5a Mon Sep 17 00:00:00 2001 From: Michael Adam Date: Wed, 28 Oct 2009 01:54:04 +0100 Subject: s3:dbwrap_ctdb: fix a race in starting concurrent transactions on a single node There are two races in concurrent transactions on a single node. One in starting a transaction and one with replay during commit. This commit closes the first race by storing the client pid in the transaction-lock record and comparing the stored pid against its own pid after releasing the lock and refetching the record inside the transaction. Michael --- source3/lib/dbwrap_ctdb.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'source3') diff --git a/source3/lib/dbwrap_ctdb.c b/source3/lib/dbwrap_ctdb.c index fce6126a5c..49df62afd3 100644 --- a/source3/lib/dbwrap_ctdb.c +++ b/source3/lib/dbwrap_ctdb.c @@ -316,12 +316,14 @@ static int db_ctdb_transaction_destructor(struct db_ctdb_transaction_handle *h) static int db_ctdb_transaction_fetch_start(struct db_ctdb_transaction_handle *h) { struct db_record *rh; + struct db_ctdb_rec *crec; TDB_DATA key; TALLOC_CTX *tmp_ctx; const char *keyname = CTDB_TRANSACTION_LOCK_KEY; int ret; struct db_ctdb_ctx *ctx = h->ctx; TDB_DATA data; + pid_t pid; NTSTATUS status; struct ctdb_ltdb_header header; @@ -337,6 +339,23 @@ again: talloc_free(tmp_ctx); return -1; } + crec = talloc_get_type_abort(rh->private_data, struct db_ctdb_rec); + + /* + * store the pid in the database: + * it is not enought that the node is dmaster... + */ + pid = getpid(); + data.dptr = (unsigned char *)&pid; + data.dsize = sizeof(pid_t); + status = db_ctdb_ltdb_store(ctx, key, &(crec->header), data); + if (!NT_STATUS_IS_OK(status)) { + DEBUG(0, (__location__ " Failed to store pid in transaction " + "record: %s\n", nt_errstr(status))); + talloc_free(tmp_ctx); + return -1; + } + talloc_free(rh); ret = tdb_transaction_start(ctx->wtdb->tdb); @@ -353,6 +372,12 @@ again: goto again; } + if ((data.dsize != sizeof(pid_t)) || (*(pid_t *)(data.dptr) != pid)) { + tdb_transaction_cancel(ctx->wtdb->tdb); + talloc_free(tmp_ctx); + goto again; + } + talloc_free(tmp_ctx); return 0; -- cgit