From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <michal.lkml@markovi.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 3/3] fixdep: do not ignore kconfig.h
Date: Wed, 28 Feb 2018 20:17:37 +0100 [thread overview]
Message-ID: <20180228191805.20094-3-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <20180228191805.20094-1-linux@rasmusvillemoes.dk>
kconfig.h was excluded from consideration by fixdep by
6a5be57f0f00 (fixdep: fix extraneous dependencies) to avoid some false
positive hits
(1) include/config/.h
(2) include/config/h.h
(3) include/config/foo.h
(1) occurred because kconfig.h contains the string CONFIG_ in a
comment. However, since dee81e988674 (fixdep: faster CONFIG_ search), we
have a check that the part after CONFIG_ is non-empty, so this does not
happen anymore (and CONFIG_ appears by itself elsewhere, so that check
is worthwhile).
(2) comes from the include guard, __LINUX_KCONFIG_H. But with the
previous patch, we no longer match that either.
That leaves (3), which amounts to one [1] false dependency (aka stat() call
done by make), which I think we can live with:
We've already had one case [2] where the lack of include/linux/kconfig.h in
the .o.cmd file caused a missing rebuild, and while I originally thought
we should just put kconfig.h in the dependency list without parsing it
for the CONFIG_ pattern, we actually do have some real CONFIG_ symbols
mentioned in it, and one can imagine some translation unit that just
does '#ifdef __BIG_ENDIAN' but doesn't through some other header
actually depend on CONFIG_CPU_BIG_ENDIAN - so changing the target
endianness could end up rebuilding the world, minus that small
TU. Quoting Linus,
... when missing dependencies cause a missed re-compile, the resulting
bugs can be _really_ subtle.
[1] well, two, we now also have CONFIG_BOOGER/booger.h - we could change
that to FOO if we care
[2] https://lkml.org/lkml/2018/2/22/838
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
scripts/basic/fixdep.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 1b21870d6e7f..449b68c4c90c 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -283,7 +283,6 @@ static int is_ignored_file(const char *s, int len)
{
return str_ends_with(s, len, "include/generated/autoconf.h") ||
str_ends_with(s, len, "include/generated/autoksyms.h") ||
- str_ends_with(s, len, "include/linux/kconfig.h") ||
str_ends_with(s, len, ".ver");
}
--
2.15.1
next prev parent reply other threads:[~2018-02-28 19:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-22 17:41 [PATCH v3] kconfig.h: Include compiler types to avoid missed struct attributes Kees Cook
2018-02-22 18:04 ` Linus Torvalds
2018-02-22 19:57 ` Kees Cook
2018-02-22 20:17 ` Linus Torvalds
2018-02-22 21:07 ` Rasmus Villemoes
2018-02-22 21:22 ` Kees Cook
2018-02-22 21:23 ` Linus Torvalds
2018-02-22 21:54 ` Linus Torvalds
2018-02-22 21:34 ` Rasmus Villemoes
2018-02-22 21:56 ` Linus Torvalds
2018-02-28 19:17 ` [PATCH 1/3] fixdep: remove stale references to uml-config.h Rasmus Villemoes
2018-02-28 19:17 ` [PATCH 2/3] fixdep: remove some false CONFIG_ matches Rasmus Villemoes
2018-02-28 19:17 ` Rasmus Villemoes [this message]
2018-03-05 4:52 ` [PATCH 3/3] fixdep: do not ignore kconfig.h Masahiro Yamada
2018-03-05 8:15 ` Rasmus Villemoes
2018-03-05 9:38 ` Masahiro Yamada
2018-03-05 14:49 ` Masahiro Yamada
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