The new thread pools code uses spinlocks.

It's mostly dead code and the original idea of worker threads has been rejected.

    *) Change: the "variables_hash_max_size" and
       "variables_hash_bucket_size" directives.

    *) Feature: the $body_bytes_sent variable can be used not only in the
       "log_format" directive.

    *) Feature: the $ssl_protocol and $ssl_cipher variables.

    *) Feature: the cache line size detection for widespread CPUs at start
       time.

    *) Feature: now the "accept_mutex" directive is supported using
       fcntl(2) on platforms different from i386, amd64, sparc64, and ppc.

    *) Feature: the "lock_file" directive and the --with-lock-path=PATH
       autoconfiguration directive.

    *) Bugfix: if the HTTPS protocol was used in the "proxy_pass" directive
       then the requests with the body was not transferred.

    *) Change: the "bl" and "af" parameters of the "listen" directive was
       renamed to the "backlog" and "accept_filter".

    *) Feature: the "rcvbuf" and "sndbuf" parameters of the "listen"
       directive.

    *) Change: the "$msec" log parameter does not require now the
       additional the gettimeofday() system call.

    *) Feature: the -t switch now tests the "listen" directives.

    *) Bugfix: if the invalid address was specified in the "listen"
       directive, then after the -HUP signal nginx left an open socket in
       the CLOSED state.

    *) Bugfix: the mime type may be incorrectly set to default value for
       index file with variable in the name; the bug had appeared in 0.3.0.

    *) Feature: the "timer_resolution" directive.

    *) Feature: the millisecond "$upstream_response_time" log parameter.

    *) Bugfix: a temporary file with client request body now is removed
       just after the response header was transferred to a client.

    *) Bugfix: OpenSSL 0.9.6 compatibility.

    *) Bugfix: the SSL certificate and key file paths could not be relative.

    *) Bugfix: the "ssl_prefer_server_ciphers" directive did not work in
       the ngx_imap_ssl_module.

    *) Bugfix: the "ssl_protocols" directive allowed to specify the single
       protocol only.

    *) Bugfix: the ngx_http_stub_status_module showed incorrect statistics
       if "rtsig" method was used or if several worker process ran on SMP.

    *) Bugfix: nginx could not be built by the icc compiler on Linux or if
       the zlib-1.2.x library was building from sources.

    *) Bugfix: nginx could not be built on NetBSD 2.0.