`make dep' with clock skew detected loops forever

Noticed something on a fresh FC16 based install on a test server in our lab. Autotest by default runs make dep and it seems the clock is pretty badly skewed on this server, resulting in an infinite loop of:

01:09:37 DEBUG| Running 'make dep'
01:09:38 DEBUG| [stderr] make: Warning: File `/usr/local/autotest/tmp/build/linux/arch/powerpc/Makefile' has modification time 112143 s in the future
01:09:38 DEBUG| [stderr] make[1]: Warning: File `/usr/local/autotest/tmp/build/linux/arch/powerpc/Makefile' has modification time 112143 s in the future
01:09:38 DEBUG| [stderr] make[2]: Warning: File `scripts/Makefile.host' has modification time 112143 s in the future
01:09:38 DEBUG| [stdout]   HOSTCC  scripts/basic/fixdep
01:09:38 DEBUG| [stderr] make[2]: warning:  Clock skew detected.  Your build may be incomplete.
01:09:38 DEBUG| [stderr] make[2]: Warning: File `scripts/Makefile.host' has modification time 112143 s in the future
01:09:38 DEBUG| [stdout]   HOSTCC  scripts/kconfig/conf.o
01:09:38 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.tab.c
01:09:38 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.lex.c
01:09:38 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.hash.c
01:09:39 DEBUG| [stdout]   HOSTCC  scripts/kconfig/zconf.tab.o
01:09:39 DEBUG| [stdout]   HOSTLD  scripts/kconfig/conf
01:09:39 DEBUG| [stdout] scripts/kconfig/conf --silentoldconfig Kconfig
01:09:39 DEBUG| [stderr] make[2]: warning:  Clock skew detected.  Your build may be incomplete.
01:09:39 DEBUG| [stderr] make[1]: warning:  Clock skew detected.  Your build may be incomplete.
01:09:39 DEBUG| [stderr] make: Warning: File `/usr/local/autotest/tmp/build/linux/arch/powerpc/Makefile' has modification time 112142 s in the future
01:09:39 DEBUG| [stderr] make[1]: Warning: File `/usr/local/autotest/tmp/build/linux/arch/powerpc/Makefile' has modification time 112142 s in the future
01:09:39 DEBUG| [stderr] make[2]: Warning: File `scripts/Makefile.host' has modification time 112142 s in the future
01:09:39 DEBUG| [stdout]   HOSTCC  scripts/basic/fixdep
01:09:40 DEBUG| [stderr] make[2]: warning:  Clock skew detected.  Your build may be incomplete.
01:09:40 DEBUG| [stderr] make[2]: Warning: File `scripts/Makefile.host' has modification time 112141 s in the future
01:09:40 DEBUG| [stdout]   HOSTCC  scripts/kconfig/conf.o
01:09:40 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.tab.c
01:09:40 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.lex.c
01:09:40 DEBUG| [stdout]   SHIPPED scripts/kconfig/zconf.hash.c
01:09:40 DEBUG| [stdout]   HOSTCC  scripts/kconfig/zconf.tab.o
01:09:40 DEBUG| [stdout]   HOSTLD  scripts/kconfig/conf
01:09:40 DEBUG| [stdout] scripts/kconfig/conf --silentoldconfig Kconfig

Anyone know why that happens? Obvious fixes are to either not run make dep or to install an NTP client, and I can do that, but figured I'd report the above.

Thanks,
Nish

Nishanth Aravamudan <[email protected]>
IBM Linux Technology Center

[...]

Because the system time time is several hours, if not days, behind, so generated files are older than source files and thus dependencies cannot work. You need to fix the system time to be at least ahead of the mtime of the sources.

I don't think this is limited to make dep.

Michal

That makes sense.

Well, killing make dep, which was just looping, and executing make -j16 vmlinux did seem to complete. But it was a while ago and maybe I'm mis-remembering.

Ah well, I've fixed up my testing scripts to ensure an ntp run is performed before trying to build.

Thanks,
Nish

Nishanth Aravamudan <[email protected]>
IBM Linux Technology Center