linux-kernel - [tip: locking/urgent] lockdep: Fix preemption WARN for spurious IRQ-enable

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Date:   Mon, 26 Oct 2020 12:41:46 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     syzbot+53f8ce8bbc07924b6417@...kaller.appspotmail.com,
        kernel test robot <lkp@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/urgent] lockdep: Fix preemption WARN for spurious IRQ-enable

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     f8e48a3dca060e80f672d398d181db1298fbc86c
Gitweb:        https://git.kernel.org/tip/f8e48a3dca060e80f672d398d181db1298fbc86c
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 22 Oct 2020 12:23:02 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 22 Oct 2020 12:37:22 +02:00

lockdep: Fix preemption WARN for spurious IRQ-enable

It is valid (albeit uncommon) to call local_irq_enable() without first
having called local_irq_disable(). In this case we enter
lockdep_hardirqs_on*() with IRQs enabled and trip a preemption warning
for using __this_cpu_read().

Use this_cpu_read() instead to avoid the warning.

Fixes: 4d004099a6 ("lockdep: Fix lockdep recursion")
Reported-by: syzbot+53f8ce8bbc07924b6417@...kaller.appspotmail.com
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/locking/lockdep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 3e99dfe..fc206ae 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4057,7 +4057,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip)
 	if (unlikely(in_nmi()))
 		return;
 
-	if (unlikely(__this_cpu_read(lockdep_recursion)))
+	if (unlikely(this_cpu_read(lockdep_recursion)))
 		return;
 
 	if (unlikely(lockdep_hardirqs_enabled())) {
@@ -4126,7 +4126,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip)
 		goto skip_checks;
 	}
 
-	if (unlikely(__this_cpu_read(lockdep_recursion)))
+	if (unlikely(this_cpu_read(lockdep_recursion)))
 		return;
 
 	if (lockdep_hardirqs_enabled()) {