Re: Compilation error for target liblockdep

From: Bart Van Assche
Date: Mon Nov 18 2019 - 18:14:11 EST

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/ 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").


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

I'm not sure what the best approach is.