`make dep' with clock skew detected loops forever

`make dep' with clock skew detected loops forever

[Nishanth Aravamudan]

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 <nacc@us.ibm.com>
IBM Linux Technology Center

Re: `make dep' with clock skew detected loops forever

[Michal Marek]

On 29.2.2012 20:01, Nishanth Aravamudan wrote:
> 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
[...]

> Anyone know why that happens?

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.


> Obvious fixes are to either not run `make dep`

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

Michal

Re: `make dep' with clock skew detected loops forever

[Nishanth Aravamudan]

On 05.03.2012 [15:40:56 +0100], Michal Marek wrote:
> On 29.2.2012 20:01, Nishanth Aravamudan wrote:
> > 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
> [...]
> 
> > Anyone know why that happens?
> 
> 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.

That makes sense.

> > Obvious fixes are to either not run `make dep`
> 
> I don't think this is limited to make dep.

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 <nacc@us.ibm.com>
IBM Linux Technology Center