linux-kernel - [PATCH 5.12 349/677] rcu: Remove spurious instrumentation_end() in rcu_nmi

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Message-Id: <20210512144848.908235260@linuxfoundation.org>
Date:   Wed, 12 May 2021 16:46:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Zhouyi Zhou <zhouzhouyi@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 349/677] rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()

From: Zhouyi Zhou <zhouzhouyi@...il.com>

[ Upstream commit 6494ccb93271bee596a12db32ff44867d5be2321 ]

In rcu_nmi_enter(), there is an erroneous instrumentation_end() in the
second branch of the "if" statement.  Oddly enough, "objtool check -f
vmlinux.o" fails to complain because it is unable to correctly cover
all cases.  Instead, objtool visits the third branch first, which marks
following trace_rcu_dyntick() as visited.  This commit therefore removes
the spurious instrumentation_end().

Fixes: 04b25a495bd6 ("rcu: Mark rcu_nmi_enter() call to rcu_cleanup_after_idle() noinstr")
Reported-by Neeraj Upadhyay <neeraju@...eaurora.org>
Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/rcu/tree.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a739c5fcca5..7356764e49a0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1077,7 +1077,6 @@ noinstr void rcu_nmi_enter(void)
 	} else if (!in_nmi()) {
 		instrumentation_begin();
 		rcu_irq_enter_check_tick();
-		instrumentation_end();
 	} else  {
 		instrumentation_begin();
 	}
-- 
2.30.2