Index: subversion/include/svn_config.h
===================================================================
--- subversion/include/svn_config.h	(revision 1618848)
+++ subversion/include/svn_config.h	(working copy)
@@ -97,6 +97,8 @@ typedef struct svn_config_t svn_config_t;
 #define SVN_CONFIG_OPTION_HTTP_MAX_CONNECTIONS      "http-max-connections"
 /** @since New in 1.9. */
 #define SVN_CONFIG_OPTION_HTTP_CHUNKED_REQUESTS     "http-chunked-requests"
+/** @since New in 1.9. */
+#define SVN_CONFIG_OPTION_HTTP_PIPELINING           "http-pipelining"
 
 /** @since New in 1.9. */
 #define SVN_CONFIG_OPTION_SERF_LOG_COMPONENTS       "serf-log-components"
Index: subversion/libsvn_ra_serf/ra_serf.h
===================================================================
--- subversion/libsvn_ra_serf/ra_serf.h	(revision 1618848)
+++ subversion/libsvn_ra_serf/ra_serf.h	(working copy)
@@ -144,6 +144,13 @@ struct svn_ra_serf__session_t {
      i.e. is there a (reverse) proxy that does not support them?  */
   svn_boolean_t detect_chunking;
 
+  /* Can serf use HTTP pipelining, or should it send requests one by one.
+     HTTP pipelining is enabled by default. The only known case where it should
+     be disabled is when the server triggers SSL renegotiations in the middle
+     of HTTP traffic on a connection, which OpenSSL currently doesn't handle
+     well. See serf issue #135. */
+  svn_boolean_t http_pipelining;
+
   /* Our Version-Controlled-Configuration; may be NULL until we know it. */
   const char *vcc_url;
 
Index: subversion/libsvn_ra_serf/serf.c
===================================================================
--- subversion/libsvn_ra_serf/serf.c	(revision 1618848)
+++ subversion/libsvn_ra_serf/serf.c	(working copy)
@@ -244,6 +244,12 @@ load_config(svn_ra_serf__session_t *session,
                                   SVN_CONFIG_OPTION_HTTP_CHUNKED_REQUESTS,
                                   "auto", svn_tristate_unknown));
 
+  /* Should we use HTTP pipelining. */
+  SVN_ERR(svn_config_get_bool(config, &session->http_pipelining,
+                              SVN_CONFIG_SECTION_GLOBAL,
+                              SVN_CONFIG_OPTION_HTTP_PIPELINING,
+                              TRUE));
+
 #if SERF_VERSION_AT_LEAST(1, 4, 0) && !defined(SVN_SERF_NO_LOGGING)
   SVN_ERR(svn_config_get_int64(config, &log_components,
                                SVN_CONFIG_SECTION_GLOBAL,
@@ -311,6 +317,12 @@ load_config(svn_ra_serf__session_t *session,
                                       SVN_CONFIG_OPTION_HTTP_CHUNKED_REQUESTS,
                                       "auto", chunked_requests));
 
+      /* Should we use HTTP pipelining. */
+      SVN_ERR(svn_config_get_bool(config, &session->http_pipelining,
+                                  server_group,
+                                  SVN_CONFIG_OPTION_HTTP_PIPELINING,
+                                  session->http_pipelining));
+
 #if SERF_VERSION_AT_LEAST(1, 4, 0) && !defined(SVN_SERF_NO_LOGGING)
       SVN_ERR(svn_config_get_int64(config, &log_components,
                                    server_group,
@@ -570,6 +582,10 @@ svn_ra_serf__open(svn_ra_session_t *session,
   if (status)
     return svn_ra_serf__wrap_err(status, NULL);
 
+  if (!serf_sess->http_pipelining) {
+      serf_connection_set_max_outstanding_requests(serf_sess->conns[0]->conn, 1);
+  }
+
   /* Set the progress callback. */
   serf_context_set_progress_cb(serf_sess->context, svn_ra_serf__progress,
                                serf_sess);
@@ -771,6 +787,10 @@ ra_serf_dup_session(svn_ra_session_t *new_session,
   if (status)
     return svn_ra_serf__wrap_err(status, NULL);
 
+  if (!new_sess->http_pipelining) {
+      serf_connection_set_max_outstanding_requests(new_sess->conns[0]->conn, 1);
+  }
+
   /* Set the progress callback. */
   serf_context_set_progress_cb(new_sess->context, svn_ra_serf__progress,
                                new_sess);
Index: subversion/libsvn_ra_serf/update.c
===================================================================
--- subversion/libsvn_ra_serf/update.c	(revision 1618848)
+++ subversion/libsvn_ra_serf/update.c	(working copy)
@@ -723,6 +723,11 @@ open_connection_if_needed(svn_ra_serf__session_t *
       if (status)
         return svn_ra_serf__wrap_err(status, NULL);
 
+      if (!sess->http_pipelining) {
+          serf_connection_set_max_outstanding_requests(sess->conns[cur]->conn,
+                                                       1);
+      }
+
       sess->num_conns++;
     }
 
Index: subversion/libsvn_subr/config_file.c
===================================================================
--- subversion/libsvn_subr/config_file.c	(revision 1618848)
+++ subversion/libsvn_subr/config_file.c	(working copy)
@@ -940,6 +940,8 @@ svn_config_ensure(const char *config_dir, apr_pool
         "###                              HTTP operation."                   NL
         "###   http-chunked-requests      Whether to use chunked transfer"   NL
         "###                              encoding for HTTP requests body."  NL
+        "###   http-pipelining            Whether to use HTTP pipelining "   NL
+        "###                              or send requests one by one."      NL
         "###   neon-debug-mask            Debug mask for Neon HTTP library"  NL
         "###   ssl-authority-files        List of files, each of a trusted CA"
                                                                              NL