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 D9DC828CF6B; Wed, 23 Apr 2025 15:16:29 +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=1745421389; cv=none; b=pLEk3Guj9qVj+jRVrb0XmpDi3CYOjP74Y/Et0bdaev6hgiPU3kKT6+VOElFpy2S0hFMvwn6frCCPJlpWthZRR4Z+O+jYxTvdRjz+xY/0anDCiyh/QNxsSHiuYVwUyZLhrExqWaKKqa/B7J8a4lY+hYElxAU63bgN+lcm//korao= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745421389; c=relaxed/simple; bh=XMUTozSxSg2oCXA1VlQdOnzOwK2sUCg0maTrksKppCw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iV+NEZSkyT42FAglcCcxXH5ymX7sFUBEK++OpkhnjV+O7SEx1abpyx/wlLYm2NB91mLSZkuWlXeu5RGgK1XAFIdK9z5ZLePXImSSqzB9diCpUeP+u8lNxLXnarlXzBN4dVXjxWHgnHT18TqS5z+d4b4Wh8pHqxoqUsHylVXKgrc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Q9qQ4TCW; 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="Q9qQ4TCW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 062D4C4CEE2; Wed, 23 Apr 2025 15:16:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1745421389; bh=XMUTozSxSg2oCXA1VlQdOnzOwK2sUCg0maTrksKppCw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q9qQ4TCWgiHKPRTkVq+0SazGRI26J96qoKDWGHaD33rPGsJUCqP2RAoiJSIsXZQbM GRD0yd/aFHoiXQgThnAYzSQnfmUiqxNAtCnQwo9xICvZvGJ8pCPGRUXJSyWf1l1apE S0JwSnF5lPp2gVJf3WJmUZdq9SEtlBqnvo0reEMU= 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 6.6 174/393] locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class() Date: Wed, 23 Apr 2025 16:41:10 +0200 Message-ID: <20250423142650.567657531@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250423142643.246005366@linuxfoundation.org> References: <20250423142643.246005366@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 6.6-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 @@ -6141,6 +6141,9 @@ 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)