Re: [tip:timers/core] time: Move timeconst.h into include/generated

[Stephen Boyd <sboyd@codeaurora.org>]

On 05/19/2015 06:36 AM, tip-bot for Nicholas Mc Guire wrote:
> Commit-ID:  0a227985d4a993a322ff72ecbaeee2611d624216
> Gitweb:     http://git.kernel.org/tip/0a227985d4a993a322ff72ecbaeee2611d624216
> Author:     Nicholas Mc Guire <hofrat@osadl.org>
> AuthorDate: Mon, 18 May 2015 14:19:12 +0200
> Committer:  Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Tue, 19 May 2015 15:13:45 +0200
>
> time: Move timeconst.h into include/generated
>
> kernel/time/timeconst.h is moved to include/generated/ and generated 
> by the top level Kbuild. This allows using timeconst.h in an earlier
> build stage.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Joe Perches <joe@perches.com>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Andrew Hunter <ahh@google.com>
> Cc: Paul Turner <pjt@google.com>
> Cc: Michal Marek <mmarek@suse.cz>
> Link: http://lkml.kernel.org/r/1431951554-5563-1-git-send-email-hofrat@osadl.org
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---

This patch seems to cause kernel/time/time.c to always need to be
recompiled and the vmlinux to be relinked even if nothing has changed.

make V=2 shows

  CC      kernel/time/time.o - due to: include/config/


> diff --git a/Kbuild b/Kbuild
> index 6f0d82a..df99a5f 100644
> --- a/Kbuild
> +++ b/Kbuild
> @@ -2,8 +2,9 @@
>  # Kbuild for top-level directory of the kernel
>  # This file takes care of the following:
>  # 1) Generate bounds.h
> -# 2) Generate asm-offsets.h (may need bounds.h)
> -# 3) Check for missing system calls
> +# 2) Generate timeconst.h
> +# 3) Generate asm-offsets.h (may need bounds.h and timeconst.h)
> +# 4) Check for missing system calls
>  
>  # Default sed regexp - multiline due to syntax constraints
>  define sed-y
> @@ -47,7 +48,26 @@ $(obj)/$(bounds-file): kernel/bounds.s FORCE
>  	$(call filechk,offsets,__LINUX_BOUNDS_H__)
>  
>  #####
> -# 2) Generate asm-offsets.h
> +# 2) Generate timeconst.h
> +
> +timeconst-file := include/generated/timeconst.h
> +
> +#always  += $(timeconst-file)

Is there a reason this is commented out instead of removed?

> +targets += $(timeconst-file)
> +
> +quiet_cmd_gentimeconst = GEN     $@
> +define cmd_gentimeconst
> [...]
> diff --git a/kernel/time/Makefile b/kernel/time/Makefile
> index 01f0312..ffc4cc3 100644
> --- a/kernel/time/Makefile
> +++ b/kernel/time/Makefile
> @@ -13,19 +13,4 @@ obj-$(CONFIG_TIMER_STATS)			+= timer_stats.o
>  obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
>  obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
>  
> -$(obj)/time.o: $(obj)/timeconst.h
> -
> -quiet_cmd_hzfile = HZFILE  $@
> -      cmd_hzfile = echo "hz=$(CONFIG_HZ)" > $@
> -
> -targets += hz.bc
> -$(obj)/hz.bc: $(objtree)/include/config/hz.h FORCE
> -	$(call if_changed,hzfile)
> -
> -quiet_cmd_bc  = BC      $@
> -      cmd_bc  = bc -q $(filter-out FORCE,$^) > $@
> -
> -targets += timeconst.h
> -$(obj)/timeconst.h: $(obj)/hz.bc $(src)/timeconst.bc FORCE
> -	$(call if_changed,bc)
> -
> +$(obj)/time.o: $(objtree)/include/config/

It looks like it has to recompile because of this dependency. Can't we
just remove this line?

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