[PATCH v2] build system: fix parallel building issue

[Michael Olbrich]

On Thu, Apr 12, 2018 at 10:07:34AM +0200, Michael Olbrich wrote:
> The files generated by the include/config/MARKER target are in the
> dependency list for applets/applet_tables.
> If applets/applet_tables is created first during applets_dir then it will
> be created again later as part of $(busybox-dirs).
> As a result include/applet_tables.h is created again. This time while other
> build commands may need it.
> 
> Let include/config/MARKER depend on applets_dir to avoid this particular
> race condition and create the header files atomically to ensure that the
> compiler never sees incomplete files.

Ignore this patch. This is bogus. The dependency must go the other way.

Regards,
Michael

> 
> Signed-off-by: Michael Olbrich <m.olbrich at pengutronix.de>
> ---
> 
> I'm not really happy with this patch, but I don't have a better idea
> either. It solves the immediate problem and should make things more
> robust.
> 
> Regards,
> Michael
> 
>  Makefile                |  2 +-
>  applets/applet_tables.c | 16 ++++++++++++++--
>  2 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 03a57adf3204..83f67bd46b50 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -851,7 +851,7 @@ quiet_cmd_gen_common_bufsiz = GEN     include/common_bufsiz.h
>  quiet_cmd_split_autoconf   = SPLIT   include/autoconf.h -> include/config/*
>        cmd_split_autoconf   = scripts/basic/split-include include/autoconf.h include/config
>  #bbox# piggybacked generation of few .h files
> -include/config/MARKER: scripts/basic/split-include include/autoconf.h
> +include/config/MARKER: scripts/basic/split-include include/autoconf.h applets_dir
>  	$(call cmd,split_autoconf)
>  	$(call cmd,gen_bbconfigopts)
>  	$(call cmd,gen_common_bufsiz)
> diff --git a/applets/applet_tables.c b/applets/applet_tables.c
> index ef911a43b36d..e3d10c83f1b9 100644
> --- a/applets/applet_tables.c
> +++ b/applets/applet_tables.c
> @@ -10,6 +10,7 @@
>  #include <sys/types.h>
>  #include <sys/stat.h>
>  #include <fcntl.h>
> +#include <limits.h>
>  #include <stdlib.h>
>  #include <string.h>
>  #include <stdio.h>
> @@ -61,6 +62,7 @@ static int str_isalnum_(const char *s)
>  int main(int argc, char **argv)
>  {
>  	int i, j;
> +	char tmp1[PATH_MAX], tmp2[PATH_MAX];
>  
>  	// In find_applet_by_name(), before linear search, narrow it down
>  	// by looking at N "equidistant" names. With ~350 applets:
> @@ -84,7 +86,8 @@ int main(int argc, char **argv)
>  
>  	if (!argv[1])
>  		return 1;
> -	i = open(argv[1], O_WRONLY | O_TRUNC | O_CREAT, 0666);
> +	snprintf(tmp1, PATH_MAX, "%s.%u.new", argv[1], (int) getpid());
> +	i = open(tmp1, O_WRONLY | O_TRUNC | O_CREAT, 0666);
>  	if (i < 0)
>  		return 1;
>  	dup2(i, 1);
> @@ -209,12 +212,21 @@ int main(int argc, char **argv)
>  //			fclose(fp);
>  //		}
>  //		if (strcmp(line_old, line_new) != 0) {
> -			fp = fopen(argv[2], "w");
> +			snprintf(tmp2, PATH_MAX, "%s.%u.new", argv[2], (int) getpid());
> +			fp = fopen(tmp2, "w");
>  			if (!fp)
>  				return 1;
>  			fputs(line_new, fp);
> +			if (fclose(fp))
> +				return 1;
>  //		}
>  	}
>  
> +	if (fclose(stdout))
> +		return 1;
> +	if (rename(tmp1, argv[1]))
> +		return 1;
> +	if (rename(tmp2, argv[2]))
> +		return 1;
>  	return 0;
>  }
> -- 
> 2.17.0
> 
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