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.