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/openbmc/linux/init/
H A DKconfig677df9d4 Sun Apr 23 11:22:05 CDT 2017 Paul E. McKenney <paulmck@linux.vnet.ibm.com> srcu: Fix Kconfig botch when SRCU not selected

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: kbuild test robot <fengguang.wu@intel.com>
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20170423162205.GP3956@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>