From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B112218C034; Thu, 17 Apr 2025 18:10:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744913454; cv=none; b=ugRVNO/Y9QgZx0Es3EOWAiaezy42f2SINyVFxvpzru5NvxRD395ux9H0LQBC0et/Oe14f2GWheZ7R/Iy1PtZg39+N7d+uNKyXts3mRo+ZNzU2n7vgU7sSdXvdmr/P6fxYXD6KTEXKwy2RmN9OBgwJ18i5yTK2bO7oI74xAexRNo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744913454; c=relaxed/simple; bh=79AGco4RLS+pIvTGaM/MSsrUh2fn8qti0Ju/pZOjUP8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MwL0JQFrw2rtphbz9qWbSY8NaRR7WsQMKeP0FKjai9t64jo+yVZ48dhTpXie4Zh/GcuHmo8fbmFQpB0zNI4Sh1knmxFaWz99QzyPpUcO4PLClnbOXVhHex5gj5Jkby7MU7+ujykbfMGVOap9UK6/4vnzpPnFNSmGvwOr9L0ucCo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xKA2RmaT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xKA2RmaT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 388C4C4CEE4; Thu, 17 Apr 2025 18:10:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744913454; bh=79AGco4RLS+pIvTGaM/MSsrUh2fn8qti0Ju/pZOjUP8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xKA2RmaTe+Gg+NADjYCwpgdzL24c33iqXtOlQkXN1Ln8k2qKrztCSRt4sqZb+hGj9 ro6ZVLD9el5J4KrcDEFHXmgaHh3y9LmS1FZEGfP/hRp/dJMPyBT/chHUyrKOjUs7/X UwMQ6FGiSWrnOXBCvYcFPCoyy9GlV6pKDBVU/gu8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Boqun Feng , Ingo Molnar , Waiman Long Subject: [PATCH 6.14 327/449] locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class() Date: Thu, 17 Apr 2025 19:50:15 +0200 Message-ID: <20250417175131.295550208@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250417175117.964400335@linuxfoundation.org> References: <20250417175117.964400335@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Boqun Feng commit 495f53d5cca0f939eaed9dca90b67e7e6fb0e30c upstream. Currently, when a lock class is allocated, nr_unused_locks will be increased by 1, until it gets used: nr_unused_locks will be decreased by 1 in mark_lock(). However, one scenario is missed: a lock class may be zapped without even being used once. This could result into a situation that nr_unused_locks != 0 but no unused lock class is active in the system, and when `cat /proc/lockdep_stats`, a WARN_ON() will be triggered in a CONFIG_DEBUG_LOCKDEP=y kernel: [...] DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused) [...] WARNING: CPU: 41 PID: 1121 at kernel/locking/lockdep_proc.c:283 lockdep_stats_show+0xba9/0xbd0 And as a result, lockdep will be disabled after this. Therefore, nr_unused_locks needs to be accounted correctly at zap_class() time. Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Reviewed-by: Waiman Long Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250326180831.510348-1-boqun.feng@gmail.com Signed-off-by: Greg Kroah-Hartman --- kernel/locking/lockdep.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -6249,6 +6249,9 @@ static void zap_class(struct pending_fre hlist_del_rcu(&class->hash_entry); WRITE_ONCE(class->key, NULL); WRITE_ONCE(class->name, NULL); + /* Class allocated but not used, -1 in nr_unused_locks */ + if (class->usage_mask == 0) + debug_atomic_dec(nr_unused_locks); nr_lock_classes--; __clear_bit(class - lock_classes, lock_classes_in_use); if (class - lock_classes == max_lock_class_idx)