core: Add support for systemtap

- First cut (configure plumbing only)
- Intended to allow people who want to test userspace
  probes for their favourite xlator(s).

Change-Id: I5bf202073a2f1cc29dc4a55714167b7f48b463a1
BUG: 865734
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/3638
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

configure.ac

@@ -362,6 +362,38 @@ AC_SUBST(SYNCDAEMON_COMPILE)
 AC_SUBST(SYNCDAEMON_SUBDIR)
 # end SYNCDAEMON section
 
+# check for systemtap/dtrace
+BUILD_SYSTEMTAP=no
+AC_MSG_CHECKING([whether to include systemtap tracing support])
+AC_ARG_ENABLE([systemtap],
+              [AS_HELP_STRING([--enable-systemtap],
+              [Enable inclusion of systemtap trace support])],
+              [ENABLE_SYSTEMTAP="${enableval}"], [ENABLE_SYSTEMTAP="def"])
+
+AM_CONDITIONAL([ENABLE_SYSTEMTAP], [test "x${ENABLE_SYSTEMTAP}" == "xyes"])
+AC_MSG_RESULT(${ENABLE_SYSTEMTAP})
+
+if test "x${ENABLE_SYSTEMTAP}" != "xno"; then
+    AC_CHECK_PROG(DTRACE, dtrace, "yes", "no")
+    AC_CHECK_HEADER([sys/sdt.h], [SDT_H_FOUND="yes"],
+                    [SDT_H_FOUND="no"])
+fi
+
+if test "x${ENABLE_SYSTEMTAP}" == "xyes"; then
+    if test "x${DTRACE}" == "xno"; then
+        AC_MSG_ERROR([dtrace not found])
+    elif test "$x{SDT_H_FOUND}" == "xno"; then
+        AC_MSG_ERROR([systemtap support needs sys/sdt.h header])
+    fi
+fi
+
+if test "x${DTRACE}" == "xyes" -a "x${SDT_H_FOUND}" == "xyes"; then
+    AC_MSG_CHECKING([x"${DTRACE}"xy"${SDT_H_FOUND}"y])
+    AC_DEFINE([HAVE_SYSTEMTAP], [1], [Define to 1 if using  probes.])
+    BUILD_SYSTEMTAP=yes
+fi
+# end of systemtap/dtrace
+
 #check if libxml is present if so enable HAVE_LIB_XML
 echo -n "checking if libxml2 is present... "
 
@@ -585,4 +617,5 @@ echo "readline           : $BUILD_READLINE"
 echo "georeplication     : $BUILD_SYNCDAEMON"
 echo "Linux-AIO          : $BUILD_LIBAIO"
 echo "Enable Debug       : $DEBUG"
+echo "systemtap          : $BUILD_SYSTEMTAP"
 echo