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From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	rostedt@goodmis.org, Alexander Aring <aahringo@redhat.com>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu 09/19] srcu: Use export for srcu_struct defined by DEFINE_STATIC_SRCU()
Date: Fri,  4 Feb 2022 15:38:52 -0800	[thread overview]
Message-ID: <20220204233902.1902-9-paulmck@kernel.org> (raw)
In-Reply-To: <20220204233858.GA1469@paulmck-ThinkPad-P17-Gen-1>

From: Alexander Aring <aahringo@redhat.com>

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>
---
 include/linux/srcutree.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 8501b6b459411..44e998643f483 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -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
-- 
2.31.1.189.g2e36527f23


  parent reply	other threads:[~2022-02-04 23:39 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-04 23:38 [PATCH rcu 0/19] SRCU updates for v5.18 Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 01/19] srcu: Tighten cleanup_srcu_struct() GP checks Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 02/19] srcu: Fix s/is/if/ typo in srcu_node comment Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 03/19] srcu: Make srcu_funnel_gp_start() cache ->mynode in snp_leaf Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 04/19] srcu: Dynamically allocate srcu_node array Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 05/19] srcu: Make Tree SRCU able to operate without snp_node array Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 06/19] srcu: Add size-state transitioning code Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 07/19] srcu: Make rcutorture dump the SRCU size state Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 08/19] srcu: Add boot-time control over srcu_node array allocation Paul E. McKenney
2022-02-04 23:38 ` Paul E. McKenney [this message]
2022-02-04 23:38 ` [PATCH rcu 10/19] srcu: Compute snp_seq earlier in srcu_funnel_gp_start() Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 11/19] srcu: Use invalid initial value for srcu_node GP sequence numbers Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 12/19] srcu: Avoid NULL dereference in srcu_torture_stats_print() Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 13/19] srcu: Prevent cleanup_srcu_struct() from freeing non-dynamic ->sda Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 14/19] srcu: Explain srcu_funnel_gp_start() call to list_add() is safe Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 15/19] srcu: Create concurrency-safe helper for initiating size transition Paul E. McKenney
2022-02-04 23:38 ` [PATCH rcu 16/19] srcu: Add contention-triggered addition of srcu_node tree Paul E. McKenney
2022-02-04 23:39 ` [PATCH rcu 17/19] srcu: Make srcu_size_state_name static Paul E. McKenney
2022-02-04 23:39 ` [PATCH rcu 18/19] srcu: Automatically determine size-transition strategy at boot Paul E. McKenney
2022-02-04 23:39 ` [PATCH rcu 19/19] srcu: Add contention check to call_srcu() srcu_data ->lock acquisition Paul E. McKenney
     [not found] ` <20220205030303.2408-1-hdanton@sina.com>
2022-02-05  5:20   ` Paul E. McKenney

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