linux-kernel - [PATCH rcu 02/23] rcu: Apply noinstr to rcu_idle_enter() and rcu_idle

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Date:   Mon, 20 Jun 2022 16:10:08 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>, Yonghong Song <yhs@...com>
Subject: [PATCH rcu 02/23] rcu: Apply noinstr to rcu_idle_enter() and rcu_idle_exit()

This commit applies the "noinstr" tag to the rcu_idle_enter() and
rcu_idle_exit() functions, which are invoked from portions of the idle
loop that cannot be instrumented.  These tags require reworking the
rcu_eqs_enter() and rcu_eqs_exit() functions that these two functions
invoke in order to cause them to use normal assertions rather than
lockdep.  In addition, within rcu_idle_exit(), the raw versions of
local_irq_save() and local_irq_restore() are used, again to avoid issues
with lockdep in uninstrumented code.

This patch is based in part on an earlier patch by Jiri Olsa, discussions
with Peter Zijlstra and Frederic Weisbecker, earlier changes by Thomas
Gleixner, and off-list discussions with Yonghong Song.

Link: https://lore.kernel.org/lkml/20220515203653.4039075-1-jolsa@kernel.org/
Reported-by: Jiri Olsa <jolsa@...nel.org>
Reported-by: Alexei Starovoitov <ast@...nel.org>
Reported-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Yonghong Song <yhs@...com>
---
 kernel/rcu/tree.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c25ba442044a6..9a5edab5558c9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -631,8 +631,8 @@ static noinstr void rcu_eqs_enter(bool user)
 		return;
 	}
 
-	lockdep_assert_irqs_disabled();
 	instrumentation_begin();
+	lockdep_assert_irqs_disabled();
 	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rcu_preempt_deferred_qs(current);
@@ -659,9 +659,9 @@ static noinstr void rcu_eqs_enter(bool user)
  * If you add or remove a call to rcu_idle_enter(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
-void rcu_idle_enter(void)
+void noinstr rcu_idle_enter(void)
 {
-	lockdep_assert_irqs_disabled();
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
 	rcu_eqs_enter(false);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -861,7 +861,7 @@ static void noinstr rcu_eqs_exit(bool user)
 	struct rcu_data *rdp;
 	long oldval;
 
-	lockdep_assert_irqs_disabled();
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
 	rdp = this_cpu_ptr(&rcu_data);
 	oldval = rdp->dynticks_nesting;
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
@@ -896,13 +896,13 @@ static void noinstr rcu_eqs_exit(bool user)
  * If you add or remove a call to rcu_idle_exit(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
-void rcu_idle_exit(void)
+void noinstr rcu_idle_exit(void)
 {
 	unsigned long flags;
 
-	local_irq_save(flags);
+	raw_local_irq_save(flags);
 	rcu_eqs_exit(false);
-	local_irq_restore(flags);
+	raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
-- 
2.31.1.189.g2e36527f23