linux-kernel - [PATCH V2 05/11] rcu: Make rcu_read_unlock

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Date: Sun,  7 Apr 2024 17:05:52 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: rcu@...r.kernel.org,
	x86@...nel.org,
	Lai Jiangshan <jiangshan.ljs@...group.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>
Subject: [PATCH V2 05/11] rcu: Make rcu_read_unlock_special() global

From: Lai Jiangshan <jiangshan.ljs@...group.com>

Make it global so that it can be used in the future inlined rcu_read_unlock().

Make it exported so that the inlined rcu_read_unlock() can be used in modules.

Make it taking a void-argument so that the caller can reduce instructions
obtaining the "current" task and it can be used in THUNK later.

Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 include/linux/rcupdate.h | 2 ++
 kernel/rcu/tree_plugin.h | 7 ++++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ebe9bfc700bb..328667ae8086 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -68,6 +68,8 @@ static inline bool same_state_synchronize_rcu(unsigned long oldstate1, unsigned
 
 #ifdef CONFIG_PREEMPT_RCU
 
+void rcu_read_unlock_special(void);
+
 void __rcu_read_lock(void);
 void __rcu_read_unlock(void);
 
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 3dbd5609185e..880b3fef1158 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -104,7 +104,6 @@ static void __init rcu_bootup_announce_oddness(void)
 
 static void rcu_report_exp_rnp(struct rcu_node *rnp, bool wake);
 static bool sync_rcu_exp_done(struct rcu_node *rnp);
-static void rcu_read_unlock_special(struct task_struct *t);
 
 #define set_rcu_preempt_special(reason)	do {				\
 	WRITE_ONCE(current->rcu_read_unlock_special.b.reason, true);	\
@@ -427,7 +426,7 @@ void __rcu_read_unlock(void)
 	if (rcu_preempt_read_exit() == 0) {
 		barrier();  // critical-section exit before .s check.
 		if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
-			rcu_read_unlock_special(t);
+			rcu_read_unlock_special();
 	}
 	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
 		int rrln = rcu_preempt_depth();
@@ -627,8 +626,9 @@ static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp)
  * notify RCU core processing or task having blocked during the RCU
  * read-side critical section.
  */
-static void rcu_read_unlock_special(struct task_struct *t)
+void rcu_read_unlock_special(void)
 {
+	struct task_struct *t = current;
 	unsigned long flags;
 	bool irqs_were_disabled;
 	bool preempt_bh_were_disabled =
@@ -684,6 +684,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
 	}
 	rcu_preempt_deferred_qs_irqrestore(t, flags);
 }
+EXPORT_SYMBOL_GPL(rcu_read_unlock_special);
 
 /*
  * Check that the list of blocked tasks for the newly completed grace
-- 
2.19.1.6.gb485710b