Compilation error for target liblockdep

Compilation error for target liblockdep

[Zhengyuan Liu]

Hi, guys,

I got a compilation error while building target liblockdep and I think I'd
better report it to you. The error info showed as bellow:

        # cd SRC/tools
        # make liblockdep
          DESCEND  lib/lockdep
          CC       lockdep.o
        In file included from lockdep.c:33:0:
        ../../../kernel/locking/lockdep.c:53:28: fatal error: linux/rcupdate.h: No such file or directory
        compilation terminated.
        mv: cannot stat './.lockdep.o.tmp': No such file or directory
        /home/lzy/kernel-upstream/linux-linus-ubuntu/tools/build/Makefile.build:96: recipe for target 'lockdep.o' failed
        make[2]: *** [lockdep.o] Error 1
        Makefile:121: recipe for target 'liblockdep-in.o' failed
        make[1]: *** [liblockdep-in.o] Error 2
        Makefile:68: recipe for target 'liblockdep' failed
        make: *** [liblockdep] Error 2

BTW, It was introduced by commit a0b0fd53e1e ("locking/lockdep: Free lock classes that are no longer in use").

Thanks.

Re: Compilation error for target liblockdep

[Bart Van Assche]

On 11/18/19 1:20 AM, Zhengyuan Liu wrote:
> I got a compilation error while building target liblockdep and I think I'd
> better report it to you. The error info showed as bellow:
> 
>          # cd SRC/tools
>          # make liblockdep
>            DESCEND  lib/lockdep
>            CC       lockdep.o
>          In file included from lockdep.c:33:0:
>          ../../../kernel/locking/lockdep.c:53:28: fatal error: linux/rcupdate.h: No such file or directory
>          compilation terminated.
>          mv: cannot stat './.lockdep.o.tmp': No such file or directory
>          /home/lzy/kernel-upstream/linux-linus-ubuntu/tools/build/Makefile.build:96: recipe for target 'lockdep.o' failed
>          make[2]: *** [lockdep.o] Error 1
>          Makefile:121: recipe for target 'liblockdep-in.o' failed
>          make[1]: *** [liblockdep-in.o] Error 2
>          Makefile:68: recipe for target 'liblockdep' failed
>          make: *** [liblockdep] Error 2
> 
> BTW, It was introduced by commit a0b0fd53e1e ("locking/lockdep: Free lock classes that are no longer in use").

(+Peter)

Hi Zhengyuan Liu,

The approach of liblockdep is fragile. Every time an additional kernel 
header is included from the lockdep code or a change is made in one of 
the kernel headers used by lockdep, that change has to be ported to the 
include files in the tools/lib/lockdep/include/liblockdep/ directory. I 
think there are two possible solutions:
- Making the changes necessary to make liblockdep build again.
- Removing the code under tools/lib/lockdep and porting this code to the
   new KUnit framework. If I understood the KUnit framework correctly it
   is based on UML and hence does not require kernel headers to be
   duplicated.

I'm not sure what the best approach is.

Thanks,

Bart.

Re: Compilation error for target liblockdep

[Bart Van Assche]

On 2020-02-13 04:59, Johannes Thumshirn wrote:
> On 18/11/2019 10:20, Zhengyuan Liu wrote:
>> Hi, guys,
>>
>> I got a compilation error while building target liblockdep and I think I'd
>> better report it to you. The error info showed as bellow:
>>
>>          # cd SRC/tools
>>          # make liblockdep
>>            DESCEND  lib/lockdep
>>            CC       lockdep.o
>>          In file included from lockdep.c:33:0:
>>          ../../../kernel/locking/lockdep.c:53:28: fatal error: linux/rcupdate.h: No such file or directory
>>          compilation terminated.
>>          mv: cannot stat './.lockdep.o.tmp': No such file or directory
>>          /home/lzy/kernel-upstream/linux-linus-ubuntu/tools/build/Makefile.build:96: recipe for target 'lockdep.o' failed
>>          make[2]: *** [lockdep.o] Error 1
>>          Makefile:121: recipe for target 'liblockdep-in.o' failed
>>          make[1]: *** [liblockdep-in.o] Error 2
>>          Makefile:68: recipe for target 'liblockdep' failed
>>          make: *** [liblockdep] Error 2
>>
>> BTW, It was introduced by commit a0b0fd53e1e ("locking/lockdep: Free lock classes that are no longer in use").
> 
> This error still pops up here on current master
> HEAD: 0bf999f9c5e74c7ecf9dafb527146601e5c848b9

I'm not sure it's worth fixing the tests under tools/lib/lockdep since
keeping these tests working requires modifying the headers under
tools/lib/lockdep/include/ every time the kernel headers under include/
are changed. How about removing tools/lib/lockdep entirely and
converting these lockdep tests to the KUnit framework? KUnit is based on
UML and I think that's a much more robust approach. For more information
about KUnit, see also https://lwn.net/Articles/780985/.

Thanks,

Bart.

Re: Compilation error for target liblockdep

[Bart Van Assche]

On 2020-04-14 06:08, Johannes Thumshirn wrote:
> These files aren't unit tests for lockdep, so they can't be converted to 
> KUnit. liblockdep is a stand alone library bringing lockdep's 
> functionallity to pthread via LDPRELOAD, see also:
> https://lwn.net/Articles/536363/

How big is the user base of liblockdep? How many alternatives exist for
liblockdep? Are these alternatives better or worse than liblockdep? See
also:
* https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
* https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual
* http://valgrind.org/docs/manual/hg-manual.html

Bart.