[PATCH] Fix early parallel make failures

From: Sam Ravnborg <sam@ravnborg.org>

Ingo said:

  Starting at around 2.6.4-rc2-mm1, I keep seeing 'scripts/fixdep: Text
  file busy' messages when doing a -j10 bzImage build - which seems to
  suggest that by the time fixdep is used by the build system it's not
  built yet.

Sam said:

I was pretty sure it was something I had caused, so I gave it a spin.  What
actually happened was that we tried to build the target 'silentoldconfig'
in parrallel with 'scripts'.  Since 'silentoldconfig' started a new make
and then the config target needed 'scripts' we saw two parallel runs.

The way I decided to fix it was to split scripts/ in two parts.  The first
part is now the very basic stuff - moved to scripts/basic/.  The second
part is dependent on kernel config etc.  and kept in scripts/

In the 2.7 timeframe i will redo this initial stuff - it's becoming too
messy for anyone to understand today.


Description:

Fix dependencies in early phases of kernel build.  This solves a few
problems nively: modpost is no longer rebuild twicewhen reaching the
'target' state 'make -j10' now works nicely again

The patch is rather large due to the following file moves:
mkdir scripts/basic
mv scripts/fixdep.c        scripts/basic
mv scripts/split-include.c scripts/basic
mv scripts/docproc.c       scripts/basic

1 files changed, 381 insertions, 0 deletions

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
new file mode 100644
index 000000000000..1e9b8d4fde38
--- /dev/null
+++ b/scripts/basic/fixdep.c
@@ -0,0 +1,381 @@
+/*
+ * "Optimize" a list of dependencies as spit out by gcc -MD
+ * for the kernel build
+ * ===========================================================================
+ *
+ * Author       Kai Germaschewski
+ * Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ *
+ *
+ * Introduction:
+ *
+ * gcc produces a very nice and correct list of dependencies which
+ * tells make when to remake a file.
+ *
+ * To use this list as-is however has the drawback that virtually
+ * every file in the kernel includes <linux/config.h> which then again
+ * includes <linux/autoconf.h>
+ *
+ * If the user re-runs make *config, linux/autoconf.h will be
+ * regenerated.  make notices that and will rebuild every file which
+ * includes autoconf.h, i.e. basically all files. This is extremely
+ * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
+ *
+ * So we play the same trick that "mkdep" played before. We replace
+ * the dependency on linux/autoconf.h by a dependency on every config
+ * option which is mentioned in any of the listed prequisites.
+ *
+ * To be exact, split-include populates a tree in include/config/,
+ * e.g. include/config/his/driver.h, which contains the #define/#undef
+ * for the CONFIG_HIS_DRIVER option.
+ *
+ * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
+ * which depend on "include/linux/config/his/driver.h" will be rebuilt,
+ * so most likely only his driver ;-)
+ *
+ * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
+ *
+ * So to get dependencies right, there two issues:
+ * o if any of the files the compiler read changed, we need to rebuild
+ * o if the command line given to the compile the file changed, we
+ *   better rebuild as well.
+ *
+ * The former is handled by using the -MD output, the later by saving
+ * the command line used to compile the old object and comparing it
+ * to the one we would now use.
+ *
+ * Again, also this idea is pretty old and has been discussed on
+ * kbuild-devel a long time ago. I don't have a sensibly working
+ * internet connection right now, so I rather don't mention names
+ * without double checking.
+ *
+ * This code here has been based partially based on mkdep.c, which
+ * says the following about its history:
+ *
+ *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
+ *   This is a C version of syncdep.pl by Werner Almesberger.
+ *
+ *
+ * It is invoked as
+ *
+ *   fixdep <depfile> <target> <cmdline>
+ *
+ * and will read the dependency file <depfile>
+ *
+ * The transformed dependency snipped is written to stdout.
+ *
+ * It first generates a line
+ *
+ *   cmd_<target> = <cmdline>
+ *
+ * and then basically copies the .<target>.d file to stdout, in the
+ * process filtering out the dependency on linux/autoconf.h and adding
+ * dependencies on include/config/my/option.h for every
+ * CONFIG_MY_OPTION encountered in any of the prequisites.
+ *
+ * It will also filter out all the dependencies on *.ver. We need
+ * to make sure that the generated version checksum are globally up
+ * to date before even starting the recursive build, so it's too late
+ * at this point anyway.
+ *
+ * The algorithm to grep for "CONFIG_..." is bit unusual, but should
+ * be fast ;-) We don't even try to really parse the header files, but
+ * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
+ * be picked up as well. It's not a problem with respect to
+ * correctness, since that can only give too many dependencies, thus
+ * we cannot miss a rebuild. Since people tend to not mention totally
+ * unrelated CONFIG_ options all over the place, it's not an
+ * efficiency problem either.
+ *
+ * (Note: it'd be easy to port over the complete mkdep state machine,
+ *  but I don't think the added complexity is worth it)
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <limits.h>
+#include <ctype.h>
+#include <netinet/in.h>
+
+#define INT_CONF ntohl(0x434f4e46)
+#define INT_ONFI ntohl(0x4f4e4649)
+#define INT_NFIG ntohl(0x4e464947)
+#define INT_FIG_ ntohl(0x4649475f)
+
+char *target;
+char *depfile;
+char *cmdline;
+
+void usage(void)
+
+{
+	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
+	exit(1);
+}
+
+void print_cmdline(void)
+{
+	printf("cmd_%s := %s\n\n", target, cmdline);
+}
+
+char * str_config  = NULL;
+int    size_config = 0;
+int    len_config  = 0;
+
+/*
+ * Grow the configuration string to a desired length.
+ * Usually the first growth is plenty.
+ */
+void grow_config(int len)
+{
+	while (len_config + len > size_config) {
+		if (size_config == 0)
+			size_config = 2048;
+		str_config = realloc(str_config, size_config *= 2);
+		if (str_config == NULL)
+			{ perror("fixdep:malloc"); exit(1); }
+	}
+}
+
+
+
+/*
+ * Lookup a value in the configuration string.
+ */
+int is_defined_config(const char * name, int len)
+{
+	const char * pconfig;
+	const char * plast = str_config + len_config - len;
+	for ( pconfig = str_config + 1; pconfig < plast; pconfig++ ) {
+		if (pconfig[ -1] == '\n'
+		&&  pconfig[len] == '\n'
+		&&  !memcmp(pconfig, name, len))
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Add a new value to the configuration string.
+ */
+void define_config(const char * name, int len)
+{
+	grow_config(len + 1);
+
+	memcpy(str_config+len_config, name, len);
+	len_config += len;
+	str_config[len_config++] = '\n';
+}
+
+/*
+ * Clear the set of configuration strings.
+ */
+void clear_config(void)
+{
+	len_config = 0;
+	define_config("", 0);
+}
+
+/*
+ * Record the use of a CONFIG_* word.
+ */
+void use_config(char *m, int slen)
+{
+	char s[PATH_MAX];
+	char *p;
+
+	if (is_defined_config(m, slen))
+	    return;
+
+	define_config(m, slen);
+
+	memcpy(s, m, slen); s[slen] = 0;
+
+	for (p = s; p < s + slen; p++) {
+		if (*p == '_')
+			*p = '/';
+		else
+			*p = tolower((unsigned char)*p);
+	}
+	printf("    $(wildcard include/config/%s.h) \\\n", s);
+}
+
+void parse_config_file(char *map, size_t len)
+{
+	int *end = (int *) (map + len);
+	/* start at +1, so that p can never be < map */
+	int *m   = (int *) map + 1;
+	char *p, *q;
+
+	for (; m < end; m++) {
+		if (*m == INT_CONF) { p = (char *) m  ; goto conf; }
+		if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
+		if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
+		if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
+		continue;
+	conf:
+		if (p > map + len - 7)
+			continue;
+		if (memcmp(p, "CONFIG_", 7))
+			continue;
+		for (q = p + 7; q < map + len; q++) {
+			if (!(isalnum(*q) || *q == '_'))
+				goto found;
+		}
+		continue;
+
+	found:
+		use_config(p+7, q-p-7);
+	}
+}
+
+/* test is s ends in sub */
+int strrcmp(char *s, char *sub)
+{
+	int slen = strlen(s);
+	int sublen = strlen(sub);
+
+	if (sublen > slen)
+		return 1;
+
+	return memcmp(s + slen - sublen, sub, sublen);
+}
+
+void do_config_file(char *filename)
+{
+	struct stat st;
+	int fd;
+	void *map;
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		fprintf(stderr, "fixdep: ");
+		perror(filename);
+		exit(2);
+	}
+	fstat(fd, &st);
+	if (st.st_size == 0) {
+		close(fd);
+		return;
+	}
+	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	if ((long) map == -1) {
+		perror("fixdep: mmap");
+		close(fd);
+		return;
+	}
+
+	parse_config_file(map, st.st_size);
+
+	munmap(map, st.st_size);
+
+	close(fd);
+}
+
+void parse_dep_file(void *map, size_t len)
+{
+	char *m = map;
+	char *end = m + len;
+	char *p;
+	char s[PATH_MAX];
+
+	p = strchr(m, ':');
+	if (!p) {
+		fprintf(stderr, "fixdep: parse error\n");
+		exit(1);
+	}
+	memcpy(s, m, p-m); s[p-m] = 0;
+	printf("deps_%s := \\\n", target);
+	m = p+1;
+
+	clear_config();
+
+	while (m < end) {
+		while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
+			m++;
+		p = m;
+		while (p < end && *p != ' ') p++;
+		if (p == end) {
+			do p--; while (!isalnum(*p));
+			p++;
+		}
+		memcpy(s, m, p-m); s[p-m] = 0;
+		if (strrcmp(s, "include/linux/autoconf.h") &&
+		    strrcmp(s, ".ver")) {
+			printf("  %s \\\n", s);
+			do_config_file(s);
+		}
+		m = p + 1;
+	}
+	printf("\n%s: $(deps_%s)\n\n", target, target);
+	printf("$(deps_%s):\n", target);
+}
+
+void print_deps(void)
+{
+	struct stat st;
+	int fd;
+	void *map;
+
+	fd = open(depfile, O_RDONLY);
+	if (fd < 0) {
+		fprintf(stderr, "fixdep: ");
+		perror(depfile);
+		exit(2);
+	}
+	fstat(fd, &st);
+	if (st.st_size == 0) {
+		fprintf(stderr,"fixdep: %s is empty\n",depfile);
+		close(fd);
+		return;
+	}
+	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	if ((long) map == -1) {
+		perror("fixdep: mmap");
+		close(fd);
+		return;
+	}
+
+	parse_dep_file(map, st.st_size);
+
+	munmap(map, st.st_size);
+
+	close(fd);
+}
+
+void traps(void)
+{
+	static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
+
+	if (*(int *)test != INT_CONF) {
+		fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
+			*(int *)test);
+		exit(2);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	traps();
+
+	if (argc != 4)
+		usage();
+
+	depfile = argv[1];
+	target = argv[2];
+	cmdline = argv[3];
+
+	print_cmdline();
+	print_deps();
+
+	return 0;
+}