lttng-modules: fix build on linux 3.14.x

By applying patch from upstream mailing list[1] (should be in the next
release).

[1]: http://lists.lttng.org/pipermail/lttng-dev/2014-December/023914.html

pkgs/os-specific/linux/lttng-modules/build-fix.patch

@@ -0,0 +1,30 @@
+[PATCH] Update compaction instrumentation for 3.14.x stable kernels
+
+Conditional compilation introduced by lttng-modules commit
+
+  0007344741ef65259bc52dea72259173dfbf96c0
+
+needs to be applied to kernels 3.14.25 and up in the 3.14.x branch.
+
+Signed-off-by: Simon Marchi <simon.marchi at polymtl.ca>
+Reported-by: Bjørn Forsman <bjorn.forsman at gmail.com>
+---
+ instrumentation/events/lttng-module/compaction.h | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/instrumentation/events/lttng-module/compaction.h b/instrumentation/events/lttng-module/compaction.h
+index ee23aa9..773a6ad 100644
+--- a/instrumentation/events/lttng-module/compaction.h
++++ b/instrumentation/events/lttng-module/compaction.h
+@@ -46,7 +46,8 @@ LTTNG_TRACEPOINT_EVENT_INSTANCE(mm_compaction_isolate_template, mm_compaction_is
+ 	TP_ARGS(nr_scanned, nr_taken)
+ )
+ 
+-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,16,0))
++#if LTTNG_KERNEL_RANGE(3,14,25, 3,15,0) || \
++	(LINUX_VERSION_CODE >= KERNEL_VERSION(3,16,0))
+ LTTNG_TRACEPOINT_EVENT(mm_compaction_migratepages,
+ 
+ 	TP_PROTO(unsigned long nr_all,
+-- 
+2.1.3

pkgs/os-specific/linux/lttng-modules/default.nix

@@ -13,6 +13,9 @@ stdenv.mkDerivation rec {
     sha256 = "01gha02ybbzr86v6s6bqn649jiw5k89kb363b9s1iv8igrdlzhl1";
   };
 
+  # from upstream ML, should be in the next release
+  patches = [ ./build-fix.patch ];
+
   preConfigure = ''
     export KERNELDIR="${kernel.dev}/lib/modules/${kernel.modDirVersion}/build"
     export INSTALL_MOD_PATH="$out"