kconfig: do not write .config if the content is the same (67424f61) · Commits · 戴 / test

Kconfig updates the .config when it exits even if its content is exactly the same as before. Since its timestamp becomes newer than that of other build artifacts, additional processing is invoked, which is annoying. - syncconfig is invoked to update include/config/auto.conf, etc. - kernel/configs.o is recompiled if CONFIG_IKCONFIG is enabled, then vmlinux is relinked as well. If the .config is not changed at all, we do not have to even touch it. Just bail out showing "No change to .config". $ make allmodconfig scripts/kconfig/conf --allmodconfig Kconfig # # configuration written to .config # $ make allmodconfig scripts/kconfig/conf --allmodconfig Kconfig # # No change to .config # Reported-by:

Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:

Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/kconfig/confdata.c

+54 −0

Original line number	Diff line number	Diff line
		@@ -3,6 +3,7 @@
		* Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
		*/

		#include <sys/mman.h>
		#include <sys/stat.h>
		#include <ctype.h>
		#include <errno.h>
		@@ -36,6 +37,52 @@ static bool is_dir(const char *path)
		return S_ISDIR(st.st_mode);
		}

		/* return true if the given two files are the same, false otherwise */
		static bool is_same(const char file1, const char file2)
		{
		int fd1, fd2;
		struct stat st1, st2;
		void map1, map2;
		bool ret = false;

		fd1 = open(file1, O_RDONLY);
		if (fd1 < 0)
		return ret;

		fd2 = open(file2, O_RDONLY);
		if (fd2 < 0)
		goto close1;

		ret = fstat(fd1, &st1);
		if (ret)
		goto close2;
		ret = fstat(fd2, &st2);
		if (ret)
		goto close2;

		if (st1.st_size != st2.st_size)
		goto close2;

		map1 = mmap(NULL, st1.st_size, PROT_READ, MAP_PRIVATE, fd1, 0);
		if (map1 == MAP_FAILED)
		goto close2;

		map2 = mmap(NULL, st2.st_size, PROT_READ, MAP_PRIVATE, fd2, 0);
		if (map2 == MAP_FAILED)
		goto close2;

		if (bcmp(map1, map2, st1.st_size))
		goto close2;

		ret = true;
		close2:
		close(fd2);
		close1:
		close(fd1);

		return ret;
		}

		/*
		* Create the parent directory of the given path.
		*
		@@ -888,6 +935,13 @@ next:
		fclose(out);

		if (*tmpname) {
		if (is_same(name, tmpname)) {
		conf_message("No change to %s", name);
		unlink(tmpname);
		sym_set_change_count(0);
		return 0;
		}

		snprintf(oldname, sizeof(oldname), "%s.old", name);
		rename(name, oldname);
		if (rename(tmpname, name))

Admin message