Date: Mon, 24 Mar 2008 22:29:43 -0400
Message-Id: <200803250229.m2P2Th2D004970@agora.fsl.cs.sunysb.edu>
From: Erez Zadok <ezk@cs.sunysb.edu>
To: linux-kernel@vger.kernel.org
Subject: non-idempotent Makefile in 2.6.25-rc6?
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2043
Lines: 68

In 2.6.24.x, after building a kernel+modules, successive runs of make do
very little:

[24]$ make
  CHK     include/linux/version.h
  CHK     include/linux/utsrelease.h
  CALL    scripts/checksyscalls.sh
  CHK     include/linux/compile.h
Kernel: arch/x86/boot/bzImage is ready  (#21)
  Building modules, stage 2.
  MODPOST 27 modules

But in v2.6.25-rc6-294-gcc7feea, re-running make seems to rebuild stuff that
may not need to be rebuilt, wasting cycles:

[25]$ make
  CHK     include/linux/version.h
  CHK     include/linux/utsrelease.h
  CALL    scripts/checksyscalls.sh
  CHK     include/linux/compile.h
  LD      vmlinux.o
  MODPOST vmlinux.o
  GEN     .version
  CHK     include/linux/compile.h
  UPD     include/linux/compile.h
  CC      init/version.o
  LD      init/built-in.o
  LD      .tmp_vmlinux1
  KSYM    .tmp_kallsyms1.S
  AS      .tmp_kallsyms1.o
  LD      .tmp_vmlinux2
  KSYM    .tmp_kallsyms2.S
  AS      .tmp_kallsyms2.o
  LD      .tmp_vmlinux3
  KSYM    .tmp_kallsyms3.S
  AS      .tmp_kallsyms3.o
  LD      vmlinux
  SYSMAP  System.map
  SYSMAP  .tmp_System.map
  CC      arch/x86/boot/version.o
  LD      arch/x86/boot/setup.elf
  OBJCOPY arch/x86/boot/setup.bin
  OBJCOPY arch/x86/boot/compressed/vmlinux.bin
  GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
  LD      arch/x86/boot/compressed/piggy.o
  LD      arch/x86/boot/compressed/vmlinux
  OBJCOPY arch/x86/boot/vmlinux.bin
  BUILD   arch/x86/boot/bzImage
Root device is (8, 1)
Setup is 11192 bytes (padded to 11264 bytes).
System is 1382 kB
Kernel: arch/x86/boot/bzImage is ready  (#215)
  Building modules, stage 2.
  MODPOST 26 modules


Why all the re-linking and such?  Is this a known issue/problem, or intended
functionality?

BTW, my files' timestamps and machine times (ntpd, etc.) are fine.

Thanks,
Erez.
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