Race condition in directory creation with parallel backups

[Alexey Kopytov]

Sometimes --parallel fails like this:

xtrabackup: Error: cannot mkdir 17: /home/alexey.kopytov/src/percona/percona-xtrabackup/test/var/backup/2011-02-12_07-26-02/sakila
xtrabackup Ver undefined Rev undefined for 5.1.53 unknown-linux-gnu (x86_64)
xtrabackup: Starting 8 threads for parallel data files transfer
innobackupex-1.5.1: Error: ibbackup child process has died at /home/alexey.kopytov/src/percona/percona-xtrabackup/Percona-Server/storage/innodb_plugin/xtrabackup/innobackupex-1.5.1 line 559.

The reason is the following code in xtrabackup.c:

  if (!my_stat(path, &stat_info, MYF(0)) &&
      my_mkdir(path,0777,MYF(0)) < 0) {
   log("xtrabackup: Error: cannot mkdir %d: %s\n",
       my_errno, path);
   return -1;

That code fails when a directory with the same name is created between my_stat() and my_mkdir() calls by a concurrent thead.

[Alexey Kopytov (akopytov)]

Steps to reproduce: run the xb_parallel test on a multi-core machine. It may take a few runs to repeat.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXB-1114