path: root/mm/ksm.c
diff options
authorNick Desaulniers <>2018-08-22 16:37:24 -0700
committerLinus Torvalds <>2018-08-22 17:31:34 -0700
commit815f0ddb346c196018d4d8f8f55c12b83da1de3f (patch)
tree4805bf7e3cb7ec4e727aba8e62f9211e9001a760 /mm/ksm.c
parent899fbc33fd775b9dfa363db28f322272920a2196 (diff)
include/linux/compiler*.h: make compiler-*.h mutually exclusive
Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6") recently exposed a brittle part of the build for supporting non-gcc compilers. Both Clang and ICC define __GNUC__, __GNUC_MINOR__, and __GNUC_PATCHLEVEL__ for quick compatibility with code bases that haven't added compiler specific checks for __clang__ or __INTEL_COMPILER. This is brittle, as they happened to get compatibility by posing as a certain version of GCC. This broke when upgrading the minimal version of GCC required to build the kernel, to a version above what ICC and Clang claim to be. Rather than always including compiler-gcc.h then undefining or redefining macros in compiler-intel.h or compiler-clang.h, let's separate out the compiler specific macro definitions into mutually exclusive headers, do more proper compiler detection, and keep shared definitions in compiler_types.h. Fixes: cafa0010cd51 ("Raise the minimum required gcc version to 4.6") Reported-by: Masahiro Yamada <> Suggested-by: Eli Friedman <> Suggested-by: Joe Perches <> Signed-off-by: Nick Desaulniers <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/ksm.c')
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 1bd514c9e5d0..5b0894b45ee5 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -652,9 +652,9 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node)
* list_head to stay clear from the rb_parent_color union
* (aligned and different than any node) and also different
* from &migrate_nodes. This will verify that future list.h changes
- * don't break STABLE_NODE_DUP_HEAD.
+ * don't break STABLE_NODE_DUP_HEAD. Only recent gcc can handle it.
-#if GCC_VERSION >= 40903 /* only recent gcc can handle it */
+#if defined(GCC_VERSION) && GCC_VERSION >= 40903
BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1);