linux-kernel - [tip: core/rcu] rcu: Remove spurious instrumentation_end() in rcu_nmi

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Date:   Sun, 11 Apr 2021 13:43:42 -0000
From:   "tip-bot2 for Zhouyi Zhou" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Zhouyi Zhou <zhouzhouyi@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/rcu] rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     6494ccb93271bee596a12db32ff44867d5be2321
Gitweb:        https://git.kernel.org/tip/6494ccb93271bee596a12db32ff44867d5be2321
Author:        Zhouyi Zhou <zhouzhouyi@...il.com>
AuthorDate:    Mon, 11 Jan 2021 09:08:59 +08:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Mon, 08 Mar 2021 14:17:35 -08:00

rcu: Remove spurious instrumentation_end() in rcu_nmi_enter()

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>
---
 kernel/rcu/tree.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e62c2de..4d90f20 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1076,7 +1076,6 @@ noinstr void rcu_nmi_enter(void)
 	} else if (!in_nmi()) {
 		instrumentation_begin();
 		rcu_irq_enter_check_tick();
-		instrumentation_end();
 	} else  {
 		instrumentation_begin();
 	}