2.3.6 MIT-pthreads Notes

This section describes some of the issues involved in using MIT-pthreads.

Note that on Linux you should not use MIT-pthreads but use the installed LinuxThreads implementation instead. See section 2.6.2 Linux Notes (All Linux Versions).

If your system does not provide native thread support, you will need to build MySQL using the MIT-pthreads package. This includes older FreeBSD systems, SunOS 4.x, Solaris 2.4 and earlier, and some others. See section 2.2.5 Operating Systems Supported by MySQL.

Note, that beginning with MySQL 4.0.2 MIT-pthreads are no longer part of the source distribution. If you require this package, you need to download it separately from http://www.mysql.com/Downloads/Contrib/pthreads-1_60_beta6-mysql.tar.gz

After downloading, extract this source archive into the top level of the MySQL source directory. It will create a new subdirectory mit-pthreads.

• On most systems, you can force MIT-pthreads to be used by running configure with the --with-mit-threads option:

  shell> ./configure --with-mit-threads
  

  Building in a non-source directory is not supported when using MIT-pthreads because we want to minimise our changes to this code.
• The checks that determine whether to use MIT-pthreads occur only during the part of the configuration process that deals with the server code. If you have configured the distribution using --without-server to build only the client code, clients will not know whether MIT-pthreads is being used and will use Unix socket connections by default. Because Unix sockets do not work under MIT-pthreads on some platforms, this means you will need to use -h or --host when you run client programs.
• When MySQL is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the --external-locking option. This is only needed if you want to be able to run two MySQL servers against the same datafiles (not recommended).
• Sometimes the pthread bind() command fails to bind to a socket without any error message (at least on Solaris). The result is that all connections to the server fail. For example:

  shell> mysqladmin version
  mysqladmin: connect to server at '' failed;
  error: 'Can't connect to mysql server on localhost (146)'
  

  The solution to this is to kill the mysqld server and restart it. This has only happened to us when we have forced the server down and done a restart immediately.
• With MIT-pthreads, the sleep() system call isn't interruptible with SIGINT (break). This is only noticeable when you run mysqladmin --sleep. You must wait for the sleep() call to terminate before the interrupt is served and the process stops.
• When linking, you may receive warning messages like these (at least on Solaris); they can be ignored:

  ld: warning: symbol `_iob' has differing sizes:
      (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
  file /usr/lib/libc.so value=0x140);
      /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken
  ld: warning: symbol `__iob' has differing sizes:
      (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
  file /usr/lib/libc.so value=0x140);
      /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken
  

• Some other warnings also can be ignored:

  implicit declaration of function `int strtoll(...)'
  implicit declaration of function `int strtoul(...)'
  

• We haven't gotten readline to work with MIT-pthreads. (This isn't needed, but may be interesting for someone.)

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