• Paul E. McKenney's avatar
    srcu: Fix Kconfig botch when SRCU not selected · 677df9d4
    Paul E. McKenney authored
    If the CONFIG_SRCU option is not selected, for example, when building
    arch/tile allnoconfig, the following build errors appear:
    
    	kernel/rcu/tree.o: In function `srcu_online_cpu':
    	tree.c:(.text+0x4248): multiple definition of `srcu_online_cpu'
    	kernel/rcu/srcutree.o:srcutree.c:(.text+0x2120): first defined here
    	kernel/rcu/tree.o: In function `srcu_offline_cpu':
    	tree.c:(.text+0x4250): multiple definition of `srcu_offline_cpu'
    	kernel/rcu/srcutree.o:srcutree.c:(.text+0x2160): first defined here
    
    The corresponding .config file shows CONFIG_TREE_SRCU=y, but no sign
    of CONFIG_SRCU, which fatally confuses SRCU's #ifdefs, resulting in
    the above errors.  The reason this occurs is the folowing line in
    init/Kconfig's definition for TREE_SRCU:
    
    	default y if !TINY_RCU && !CLASSIC_SRCU
    
    If CONFIG_CLASSIC_SRCU=n, as it will be in for allnoconfig, and if
    CONFIG_SMP=y, then we will get CONFIG_TREE_SRCU=y but no CONFIG_SRCU,
    as seen in the .config file, and which will result in the above errors.
    This error did not show up during rcutorture testing because rcutorture
    forces CONFIG_SRCU=y, as it must to prevent build errors in rcutorture.c.
    
    This commit therefore conditions TREE_SRCU (and TINY_SRCU, while it is
    at it) with SRCU, like this:
    
    	default y if SRCU && !TINY_RCU && !CLASSIC_SRCU
    Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
    Reported-by: default avatarIngo Molnar <mingo@kernel.org>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Link: http://lkml.kernel.org/r/20170423162205.GP3956@linux.vnet.ibm.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    677df9d4
Kconfig 70.5 KB