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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@meta.com,
        rostedt@goodmis.org, hch@lst.de,
        "Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH RFC rcu 07/19] srcu: Move ->lock initialization after srcu_usage allocation
Date:   Thu, 23 Mar 2023 17:19:26 -0700
Message-Id: <20230324001938.3443499-7-paulmck@kernel.org>
In-Reply-To: <3db82572-f156-4a5d-b711-841aa28bd996@paulmck-laptop>
References: <3db82572-f156-4a5d-b711-841aa28bd996@paulmck-laptop>
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Currently, both __init_srcu_struct() in CONFIG_DEBUG_LOCK_ALLOC=y kernels
and init_srcu_struct() in CONFIG_DEBUG_LOCK_ALLOC=n kernel initialize
the srcu_struct structure's ->lock before the srcu_usage structure has
been allocated.  This of course prevents the ->lock from being moved
to the srcu_usage structure, so this commit moves the initialization
into the init_srcu_struct_fields() after the srcu_usage structure has
been allocated.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
---
 kernel/rcu/srcutree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 6b6d92fe41cf..f6f37e34a1e0 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -240,6 +240,8 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
 		ssp->srcu_sup = kzalloc(sizeof(*ssp->srcu_sup), GFP_KERNEL);
 	if (!ssp->srcu_sup)
 		return -ENOMEM;
+	if (!is_static)
+		spin_lock_init(&ACCESS_PRIVATE(ssp, lock));
 	ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
 	ssp->srcu_sup->node = NULL;
 	mutex_init(&ssp->srcu_sup->srcu_cb_mutex);
@@ -285,7 +287,6 @@ int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
 	/* Don't re-initialize a lock while it is held. */
 	debug_check_no_locks_freed((void *)ssp, sizeof(*ssp));
 	lockdep_init_map(&ssp->dep_map, name, key, 0);
-	spin_lock_init(&ACCESS_PRIVATE(ssp, lock));
 	return init_srcu_struct_fields(ssp, false);
 }
 EXPORT_SYMBOL_GPL(__init_srcu_struct);
@@ -302,7 +303,6 @@ EXPORT_SYMBOL_GPL(__init_srcu_struct);
  */
 int init_srcu_struct(struct srcu_struct *ssp)
 {
-	spin_lock_init(&ACCESS_PRIVATE(ssp, lock));
 	return init_srcu_struct_fields(ssp, false);
 }
 EXPORT_SYMBOL_GPL(init_srcu_struct);
-- 
2.40.0.rc2