From patchwork Fri Feb 23 12:44:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Cameron X-Patchwork-Id: 13569024 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (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 6A70873F0A; Fri, 23 Feb 2024 12:45:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708692306; cv=none; b=jpSMV1pivRbgmm4AXGHxtpffhigaV/jUhbFXnwtGhG2cAEPxHDEzDw4lNhQ4qUFE8kLHrZ5aW/3j+8+ZCcYhBUGN194BnNMFTsWIHQuwlfgqpeH5VjRr5FBOlq+d6tqw5DP65QUYdXyASPHp3drKWaQrpAPqgrkJmW4RSNJcayQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708692306; c=relaxed/simple; bh=/P0d7MsaVNdBlLfUwWZoHt7wXeT0BkNvQZy0Rn68npo=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KNR/9z0L4Hramv53OHGv8xWvYfTs67M4+ax9sc2iir3TxslS1ci+9kstEHSCuVrTHQPURCAcADNvhossySIO2d3O3grnzsO2NTiJAlPsJ1XFPOfLqeHBNHKGztLjKQQjmRagZw520i1FPfzxOI6WSaXwF3c+lUlSHrsP3Ik97Hc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Th8l56j03z6K8wg; Fri, 23 Feb 2024 20:41:21 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id E6723140119; Fri, 23 Feb 2024 20:45:00 +0800 (CST) Received: from SecurePC-101-06.china.huawei.com (10.122.247.231) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Fri, 23 Feb 2024 12:45:00 +0000 From: Jonathan Cameron To: , Rob Herring , Frank Rowand , , Julia Lawall CC: Peter Zijlstra , Andy Shevchenko , Greg Kroah-Hartman , Subject: [PATCH v2 1/4] of: Add cleanup.h based auto release via __free(device_node) markings. Date: Fri, 23 Feb 2024 12:44:29 +0000 Message-ID: <20240223124432.26443-2-Jonathan.Cameron@huawei.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240223124432.26443-1-Jonathan.Cameron@huawei.com> References: <20240223124432.26443-1-Jonathan.Cameron@huawei.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: lhrpeml100004.china.huawei.com (7.191.162.219) To lhrpeml500005.china.huawei.com (7.191.163.240) The recent addition of scope based cleanup support to the kernel provides a convenient tool to reduce the chances of leaking reference counts where of_node_put() should have been called in an error path. This enables struct device_node *child __free(device_node) = NULL; for_each_child_of_node(np, child) { if (test) return test; } with no need for a manual call of of_node_put(). A following patch will reduce the scope of the child variable to the for loop, to avoid an issues with ordering of autocleanup, and make it obvious when this assigned a non NULL value. In this simple example the gains are small but there are some very complex error handling cases buried in these loops that will be greatly simplified by enabling early returns with out the need for this manual of_node_put() call. Note that there are coccinelle checks in scripts/coccinelle/iterators/for_each_child.cocci to detect a failure to call of_node_put(). This new approach does not cause false positives. Longer term we may want to add scripting to check this new approach is done correctly with no double of_node_put() calls being introduced due to the auto cleanup. It may also be useful to script finding places this new approach is useful. Signed-off-by: Jonathan Cameron --- include/linux/of.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/of.h b/include/linux/of.h index 6a9ddf20e79a..50e882ee91da 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -13,6 +13,7 @@ */ #include #include +#include #include #include #include @@ -134,6 +135,7 @@ static inline struct device_node *of_node_get(struct device_node *node) } static inline void of_node_put(struct device_node *node) { } #endif /* !CONFIG_OF_DYNAMIC */ +DEFINE_FREE(device_node, struct device_node *, if (_T) of_node_put(_T)) /* Pointer for first entry in chain of all nodes. */ extern struct device_node *of_root;