linux-kernel - [PATCH rcu 01/11] rcu/nocb: Introduce RCU_NOCB_LOCKDEP

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Message-Id: <20240816045608.30564-2-neeraj.upadhyay@kernel.org>
Date: Fri, 16 Aug 2024 10:25:58 +0530
From: neeraj.upadhyay@...nel.org
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	rostedt@...dmis.org,
	paulmck@...nel.org,
	neeraj.upadhyay@...nel.org,
	neeraj.upadhyay@....com,
	boqun.feng@...il.com,
	joel@...lfernandes.org,
	urezki@...il.com,
	frederic@...nel.org
Subject: [PATCH rcu 01/11] rcu/nocb: Introduce RCU_NOCB_LOCKDEP_WARN()

From: Frederic Weisbecker <frederic@...nel.org>

Checking for races against concurrent (de-)offloading implies the
creation of !CONFIG_RCU_NOCB_CPU stubs to check if each relevant lock
is held. For now this only implies the nocb_lock but more are to be
expected.

Create instead a NOCB specific version of RCU_LOCKDEP_WARN() to avoid
the proliferation of stubs.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@...nel.org>
---
 include/linux/rcupdate.h |  7 +++++++
 kernel/rcu/tree_nocb.h   | 14 --------------
 kernel/rcu/tree_plugin.h |  4 ++--
 3 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 13f6f00aecf9..d48d3c237305 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -144,11 +144,18 @@ void rcu_init_nohz(void);
 int rcu_nocb_cpu_offload(int cpu);
 int rcu_nocb_cpu_deoffload(int cpu);
 void rcu_nocb_flush_deferred_wakeup(void);
+
+#define RCU_NOCB_LOCKDEP_WARN(c, s) RCU_LOCKDEP_WARN(c, s)
+
 #else /* #ifdef CONFIG_RCU_NOCB_CPU */
+
 static inline void rcu_init_nohz(void) { }
 static inline int rcu_nocb_cpu_offload(int cpu) { return -EINVAL; }
 static inline int rcu_nocb_cpu_deoffload(int cpu) { return 0; }
 static inline void rcu_nocb_flush_deferred_wakeup(void) { }
+
+#define RCU_NOCB_LOCKDEP_WARN(c, s)
+
 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
 
 /*
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 3ce30841119a..f4112fc663a7 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -16,10 +16,6 @@
 #ifdef CONFIG_RCU_NOCB_CPU
 static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
 static bool __read_mostly rcu_nocb_poll;    /* Offload kthread are to poll. */
-static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
-{
-	return lockdep_is_held(&rdp->nocb_lock);
-}
 
 static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
 {
@@ -1653,16 +1649,6 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
 
 #else /* #ifdef CONFIG_RCU_NOCB_CPU */
 
-static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
-{
-	return 0;
-}
-
-static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
-{
-	return false;
-}
-
 /* No ->nocb_lock to acquire.  */
 static void rcu_nocb_lock(struct rcu_data *rdp)
 {
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c569da65b421..f752b2a1d887 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -24,10 +24,10 @@ static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
 	 * timers have their own means of synchronization against the
 	 * offloaded state updaters.
 	 */
-	RCU_LOCKDEP_WARN(
+	RCU_NOCB_LOCKDEP_WARN(
 		!(lockdep_is_held(&rcu_state.barrier_mutex) ||
 		  (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_held()) ||
-		  rcu_lockdep_is_held_nocb(rdp) ||
+		  lockdep_is_held(&rdp->nocb_lock) ||
 		  (!(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preemptible()) &&
 		   rdp == this_cpu_ptr(&rcu_data)) ||
 		  rcu_current_is_nocb_kthread(rdp)),
-- 
2.40.1