linux-kernel - [PATCH][RFC] lockdep: improve comments in wait-type checks

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Date:   Wed, 11 Aug 2021 05:03:19 +0800
From:   Zhouyi Zhou <zhouzhouyi@...il.com>
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com, paulmck@...nel.org,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org, linux-kernel@...r.kernel.org,
        rcu@...r.kernel.org
Cc:     Zhouyi Zhou <zhouzhouyi@...il.com>
Subject: [PATCH][RFC] lockdep: improve comments in wait-type checks

Hi Peter,
  I think comments in wait-type checks may benifit from some comments
improvement.
  I recklessly add Paul to signed-off-by, because I asked his opinion
about comment in rcu_read_lock_bh part.

Thanks a lot
Zhouyi

Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 include/linux/lockdep_types.h | 2 +-
 kernel/locking/lockdep.c      | 2 +-
 kernel/rcu/update.c           | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index 3e726ace5c62..d22430840b53 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -21,7 +21,7 @@ enum lockdep_wait_type {
 	LD_WAIT_SPIN,		/* spin loops, raw_spinlock_t etc.. */
 
 #ifdef CONFIG_PROVE_RAW_LOCK_NESTING
-	LD_WAIT_CONFIG,		/* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */
+	LD_WAIT_CONFIG,		/* preemptible in PREEMPT_RT, spinlock_t etc.. */
 #else
 	LD_WAIT_CONFIG = LD_WAIT_SPIN,
 #endif
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index bf1c00c881e4..952d0ccf8776 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4671,7 +4671,7 @@ print_lock_invalid_wait_context(struct task_struct *curr,
 /*
  * Verify the wait_type context.
  *
- * This check validates we takes locks in the right wait-type order; that is it
+ * This check validates we take locks in the right wait-type order; that is it
  * ensures that we do not take mutexes inside spinlocks and do not attempt to
  * acquire spinlocks inside raw_spinlocks and the sort.
  *
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index c21b38cc25e9..690b0cec7459 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -247,7 +247,7 @@ struct lockdep_map rcu_lock_map = {
 	.name = "rcu_read_lock",
 	.key = &rcu_lock_key,
 	.wait_type_outer = LD_WAIT_FREE,
-	.wait_type_inner = LD_WAIT_CONFIG, /* XXX PREEMPT_RCU ? */
+	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
 };
 EXPORT_SYMBOL_GPL(rcu_lock_map);
 
@@ -256,7 +256,7 @@ struct lockdep_map rcu_bh_lock_map = {
 	.name = "rcu_read_lock_bh",
 	.key = &rcu_bh_lock_key,
 	.wait_type_outer = LD_WAIT_FREE,
-	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_LOCK also makes BH preemptible */
+	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
 };
 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
 
-- 
2.25.1