Index: subversion/libsvn_fs_util/sqlite-util.c
===================================================================
--- subversion/libsvn_fs_util/sqlite-util.c	(revision 27961)
+++ subversion/libsvn_fs_util/sqlite-util.c	(working copy)
@@ -26,6 +26,7 @@
 
 #include <sqlite3.h>
 
+#include "svn_types.h"
 #include "svn_fs.h"
 #include "svn_path.h"
 #include "svn_mergeinfo.h"
@@ -185,11 +186,45 @@
                             sqlite3_errmsg(db));
 }
 
+#ifndef SVN_HAVE_SQLITE_THREADSAFE_PREDICATE
+#include <dlfcn.h>
+#endif
+
 svn_error_t *
 svn_fs__sqlite_open(sqlite3 **db, const char *repos_path, apr_pool_t *pool)
 {
-  const char *db_path = svn_path_join(repos_path,
-                                      SVN_FS__SQLITE_DB_NAME, pool);
+  const char *db_path;
+  svn_boolean_t is_threadsafe = TRUE;
+
+  /* SQLite 3.5 allows verification of its thread-safety at runtime.
+     Older versions are simply expected to have been compiled with
+     -DSQLITE_THREADSAFE=1 or -DTHREADSAFE. */
+#ifdef SVN_HAVE_SQLITE_THREADSAFE_PREDICATE
+  is_threadsafe = sqlite3_threadsafe();
+#else
+  /* Attempt to dynamically load sqlite3_threadsafe().  Since it
+     wasn't statically compiled into Subversion, the version of SQLite
+     present at compile-time may've changed.. */
+  void *lib_handle = dlopen("libsqlite3.so", RTLD_NOW);
+  if (lib_handle)
+    {
+      int (*threadsafe_func)(void) = dlsym(lib_handle, "sqlite3_threadsafe");
+      if (threadsafe_func)
+        is_threadsafe = (*threadsafe_func)();
+      dlclose(lib_handle);
+    }
+
+  /* Clear any the dynamic library-related failure. */
+  dlerror();
+#endif
+  if (! is_threadsafe)
+    return svn_error_create(SVN_ERR_FS_SQLITE_ERROR, NULL,
+                            _("SQLite is required to be compiled and run in "
+                              "thread-safe mode"));
+
+  db_path = svn_path_join(repos_path, SVN_FS__SQLITE_DB_NAME, pool);
+
+  /* Open the database. */
   SVN_FS__SQLITE_ERR(sqlite3_open(db_path, db), *db);
   /* Retry until timeout when database is busy. */
   SVN_FS__SQLITE_ERR(sqlite3_busy_timeout(*db, BUSY_TIMEOUT), *db);
Index: build/ac-macros/sqlite.m4
===================================================================
--- build/ac-macros/sqlite.m4	(revision 27961)
+++ build/ac-macros/sqlite.m4	(working copy)
@@ -52,6 +52,8 @@
           svn_lib_sqlite="yes"
           SVN_SQLITE_INCLUDES="`$pkg_config $SQLITE_PKGNAME --cflags`"
           SVN_SQLITE_LIBS="`$pkg_config $SQLITE_PKGNAME --libs`"
+          AC_CHECK_LIB(sqlite3, sqlite3_threadsafe,
+                       [threadsafety_runtime_check_avail=yes])
           ;;
         *)
           AC_MSG_RESULT([none or unsupported $sqlite_version])
@@ -68,6 +70,11 @@
     fi
   ])
 
+  if test "$threadsafety_runtime_check_avail" = "yes"; then
+    AC_DEFINE([SVN_HAVE_SQLITE_THREADSAFE_PREDICATE], [1],
+      [Defined if SQLite 3.5+'s thread-safety runtime check is available.])
+  fi
+
   AC_SUBST(SVN_SQLITE_INCLUDES)
   AC_SUBST(SVN_SQLITE_LIBS)
 ])
@@ -94,8 +101,12 @@
         else
           SVN_SQLITE_LIBS="-lsqlite3"
         fi
-      ]) ])
 
+        AC_CHECK_LIB(sqlite3, sqlite3_threadsafe,
+                     [threadsafety_runtime_check_avail=yes])
+      ])
+    ])
+
   if test "$sqlite_dir" != "" && test -d "$sqlite_dir"; then
     CPPFLAGS="$save_CPPFLAGS"
     LDFLAGS="$save_LDFLAGS"