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 39F0A25525C; Thu, 17 Apr 2025 18:51:44 +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=1744915905; cv=none; b=MNDyJPjERtDeJC+LAfSGR+WbaMbs+eq19vRikcOYsnJPuiSA3BdftQO2daAwBrkREaSETL5Hb7G9gN3BCijaioeDynKumdlACnR8asflF7hoeEqW8YmrB/IFq66ROSDThY6QmZd89o3cuEv//M+Baj2qIn7v8gBneAWvt7BRJ34= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744915905; c=relaxed/simple; bh=ItF+ole/2C2yIz546BP5na7eBWvQf83YE8ij0FlUIbI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tPosBF5fCEvp1dyao6DQKUSIZO1ZvpSq5GUZ+hTMaqw9ZyOBCuNJDsIfoQSuzJe2UF1VHB7sgOQmkip8VzV7iWbgqZK/QRdY/ccWbvu59ywbRwkcp3wKaPlzL/N3j74Dyyb0kDNgH14bOg87KDs5cZ9AdOssonxF8OJTMQ/SiVU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dTnzhQdF; 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="dTnzhQdF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5EB7FC4CEE4; Thu, 17 Apr 2025 18:51:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744915904; bh=ItF+ole/2C2yIz546BP5na7eBWvQf83YE8ij0FlUIbI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dTnzhQdF8ml81LhlSmMoPjOouYNZoTiC18RvOAxzqGUbFB7NyFGYjbXaHcuvAjOmv P63IUnAA8QqDVYb0wbnKbPlBUdn5DESoRt0Ed30SWb5pmO3aX6J7AvF/Ipl5a87ZXj wmZKkMJkV+sW+uy+nVtsMKDw0NUFHZH5FVR/tIVI= 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 6.12 278/393] locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class() Date: Thu, 17 Apr 2025 19:51:27 +0200 Message-ID: <20250417175118.792098689@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250417175107.546547190@linuxfoundation.org> References: <20250417175107.546547190@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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 @@ -6223,6 +6223,9 @@ 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)