Commit 677df9d4 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar

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: default avatarkbuild test robot <>
Reported-by: default avatarIngo Molnar <>
Signed-off-by: default avatarPaul E. McKenney <>
Link: default avatarIngo Molnar <>
parent 58d30c36
......@@ -545,13 +545,13 @@ config CLASSIC_SRCU
config TINY_SRCU
default y if TINY_RCU && !CLASSIC_SRCU
default y if SRCU && TINY_RCU && !CLASSIC_SRCU
This option selects the single-CPU non-preemptible version of SRCU.
config TREE_SRCU
default y if !TINY_RCU && !CLASSIC_SRCU
default y if SRCU && !TINY_RCU && !CLASSIC_SRCU
This option selects the full-fledged version of SRCU.
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