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srcu: Use export for srcu_struct defined by DEFINE_STATIC_SRCU()

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If an srcu_struct structure defined by tree SRCU's DEFINE_STATIC_SRCU()
is used by a module, sparse will give the following diagnostic:

sparse: symbol '__srcu_struct_nodes_srcu' was not declared. Should it be static?

The problem is that a within-module DEFINE_STATIC_SRCU() must define
a non-static srcu_struct because it is exported by referencing it in a
special '__section("___srcu_struct_ptrs")'.  This reference is needed
so that module load and unloading can invoke init_srcu_struct() and
cleanup_srcu_struct(), respectively.  Unfortunately, sparse is unaware of
'__section("___srcu_struct_ptrs")', resulting in the above false-positive
diagnostic.  To avoid this false positive, this commit therefore creates
a prototype of the srcu_struct with an "extern" keyword.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Alexander Aring 2022-01-26 10:03:54 -05:00 committed by Paul E. McKenney
parent c69a00a12e
commit db8f1471c6
1 changed files with 1 additions and 0 deletions
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include/linux/srcutree.h
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@ -131,6 +131,7 @@ struct srcu_struct {
#ifdef MODULE
# define __DEFINE_SRCU(name, is_static) \
is_static struct srcu_struct name; \
extern struct srcu_struct * const __srcu_struct_##name; \
struct srcu_struct * const __srcu_struct_##name \
__section("___srcu_struct_ptrs") = &name
#else