[Buildroot] [PATCH] ubifs: Fix regression in ubifs_readdir()

[Arnout Vandecappelle <arnout@mind.be>]

On 03-11-16 08:23, J?rg Krause wrote:
> On Thu, 2016-11-03 at 03:46 +0100, Arnout Vandecappelle wrote:
>>
>> On 02-11-16 23:49, J?rg Krause wrote:
[snip]
>>>>> Yes, I am. Linux kernel source directory is located locally and
>>>>> the
>>>>> path is set using LINUX_OVERRIDE_SRCDIR in local.mk.
>>>>>
>>>>> 1/ Checkout Linux kernel version 4.7.10
>>>>> 2/ make linux-dirclean all
>>>>> 3/ Booted Linux version is 4.7.10
>>>>>
>>>>> 4/ Checkout Linux kernel version 4.8.5
>>>>> 5/ make linux-dirclean all
>>>>> 6/ Booted Linux version is still 4.7.10
>>>>
>>>> And this scenario works fine with ccache *disabled*, but breaks
>>>> when
>>>> you enable ccache support in Buildroot?
>>>
>>> Yes.
>>
>>  I can't reproduce this. I've got a nice mix of cache misses and
>> cache hits when
>> building a different version, and version.o is definitely a cache
>> miss.
>>
>>  Can you double-check the version in output/build/linux-
>> custom/init/version.o?
> 
> I checked the version string in version.o with hexdump -C and they
> differ.

 And the version that is in there is correct, right? (Use strings to get it, the
first string it finds should be the version string as in uname -a).

 This is very weird, because version.o gets linked into the vmlinux.elf and
eventually the zImage, and ccache doesn't get activated anymore in that path
because it's all linking and no compiling...

> 
>> And the one in output/build/linux-
>> custom/include/generated/utsrelease.h?
> 
> This as well.
> 
>>  Hm, hang on, is there maybe a utsrelease.h that ends up in your
>> staging dir and that is used by ccache?
> 
> No, there is only the linux generated file.
> 
> ---
> 
> I am not experienced with ccache, but I got some statistics:
> 
> I cleared the cache by removing ~/.buildroot-ccache, than run `make
> linux-dirclean linux`:
> 
> cache hit (direct)                     0
> cache hit (preprocessed)               0
> cache miss                          1088
> cache hit rate                      0.00 %
> called for link                       10
> called for preprocessing               5
> no input file                        394
> cleanups performed                     0
> files in cache                      3250
> 
> Then I re-run `make linux-dirclean linux` (without altering the linux
> sources):
> 
> cache hit (direct)                  1076
> cache hit (preprocessed)              10
> cache miss                          1090
> cache hit rate                     49.91 %
> called for link                       20
> called for preprocessing              10
> no input file                        788
> cleanups performed                     0
> files in cache                      3264
> 
> Again, clear the cache and run `make linux-dirclean linux`, but alter
> the linux sources by checking out a different branch:
> 
> cache hit (direct)                    10

 This is weird, it shouldn't go down... Did you clear the cache or the
statistics somewhere in between?

> cache hit (preprocessed)              62
> cache miss                          2102
> cache hit rate                      3.31 %
> called for link                       20
> called for preprocessing              10
> no input file                        773
> cleanups performed                     0
> files in cache                      6386
> 
> ---
> 
> Furthermore, I did the following for the different linux builds:
> 
> After building branch-4.7.y:
> # cp output/build/linux-custom/arch/arm/boot/zImage zImage-4.7.10
> 
> After building branch-4.8.y:
> # cp output/build/linux-custom/arch/arm/boot/zImage zImage-4.8.5
> 
> Afterwards, diff shows no differences:
> # diff zImage-4.7.10 zImage-4.8.5

 Since version.o differs, it means the version.o doesn't end up in the zImage...
Again, can you check for the intermediate files what happens to them? E.g.
init/built-in.o, .tmp_vmlinux1, arch/arm/boot/Image. Maybe just do "mv
output/build/linux-custom output/build/linux-custom.orig" before rebuilding and
do a full tree compare to find which files are identical.

 Regards,
 Arnout

> 
> Best regards,
> J?rg Krause
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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