From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4337CC43381 for ; Mon, 1 Apr 2019 17:47:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E6E620830 for ; Mon, 1 Apr 2019 17:47:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554140840; bh=ZrYRu+KzVZ9sDLamHmf+86m8060dm5AcAEW+8GFR7kI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=prgjnyxnePGB/yzThtO1mbzHs/dEuPTw7mS2ULnVehbeEtJW0uq9A0iUWlb3uZQdo xJsFmpJjT068aFUW4kCGN5+8dgLzkjjXu2uVZDKMG3dOyYeHfbzzJrnNwS2IlVQMp6 w4fYgh9eO5n0nxkw6OK7nJZlZ7q501MhHDTd9E9w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733009AbfDARcW (ORCPT ); Mon, 1 Apr 2019 13:32:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:40444 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387467AbfDARcW (ORCPT ); Mon, 1 Apr 2019 13:32:22 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 84E9620880; Mon, 1 Apr 2019 17:32:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554139941; bh=ZrYRu+KzVZ9sDLamHmf+86m8060dm5AcAEW+8GFR7kI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qMMybO2ftffdkg++mAPpVZEqwJkOXzaKzh6Pinlk1hWo/GL9NHaGa71xtPwhVmguC fin3cqn536Wq3cDHsuihfjL9kCzMi/r+hTpf9OnRo/baFC0LhaGHuDbNzSmGMczgYy 9zW9IlKMSEC04N4UYx6vPoflBUoyegMBGc/DwfWk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Shishkin , Sasha Levin Subject: [PATCH 4.4 059/131] stm class: Fix link list locking Date: Mon, 1 Apr 2019 19:02:09 +0200 Message-Id: <20190401170057.249309376@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190401170051.645954551@linuxfoundation.org> References: <20190401170051.645954551@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit c74f7e8281add80bdfa0ad2998b8df287b13df73 ] Currently, the list of stm_sources linked to an stm device is protected by a spinlock, which also means that sources' .unlink() method is called under this spinlock. However, this method may (and does) sleep, which means trouble. This patch slightly reworks locking around stm::link_list so that bits that might_sleep() are called with a mutex held instead. Modification of this list requires both mutex and spinlock to be held, while looking at the list can be done under either mutex or spinlock. Signed-off-by: Alexander Shishkin Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/hwtracing/stm/core.c | 38 +++++++++++++++++++++++++++--------- drivers/hwtracing/stm/stm.h | 1 + 2 files changed, 30 insertions(+), 9 deletions(-) diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index 92ab51aa8a74..f286de2e86af 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -647,6 +647,7 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data, if (err) goto err_device; + mutex_init(&stm->link_mutex); spin_lock_init(&stm->link_lock); INIT_LIST_HEAD(&stm->link_list); @@ -677,11 +678,11 @@ void stm_unregister_device(struct stm_data *stm_data) struct stm_source_device *src, *iter; int i; - spin_lock(&stm->link_lock); + mutex_lock(&stm->link_mutex); list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) { __stm_source_link_drop(src, stm); } - spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); synchronize_srcu(&stm_source_srcu); @@ -700,6 +701,17 @@ void stm_unregister_device(struct stm_data *stm_data) } EXPORT_SYMBOL_GPL(stm_unregister_device); +/* + * stm::link_list access serialization uses a spinlock and a mutex; holding + * either of them guarantees that the list is stable; modification requires + * holding both of them. + * + * Lock ordering is as follows: + * stm::link_mutex + * stm::link_lock + * src::link_lock + */ + /** * stm_source_link_add() - connect an stm_source device to an stm device * @src: stm_source device @@ -716,6 +728,7 @@ static int stm_source_link_add(struct stm_source_device *src, char *id; int err; + mutex_lock(&stm->link_mutex); spin_lock(&stm->link_lock); spin_lock(&src->link_lock); @@ -725,6 +738,7 @@ static int stm_source_link_add(struct stm_source_device *src, spin_unlock(&src->link_lock); spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); id = kstrdup(src->data->name, GFP_KERNEL); if (id) { @@ -762,6 +776,7 @@ static int stm_source_link_add(struct stm_source_device *src, stm_put_device(stm); fail_detach: + mutex_lock(&stm->link_mutex); spin_lock(&stm->link_lock); spin_lock(&src->link_lock); @@ -770,6 +785,7 @@ static int stm_source_link_add(struct stm_source_device *src, spin_unlock(&src->link_lock); spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); return err; } @@ -782,13 +798,20 @@ static int stm_source_link_add(struct stm_source_device *src, * If @stm is @src::link, disconnect them from one another and put the * reference on the @stm device. * - * Caller must hold stm::link_lock. + * Caller must hold stm::link_mutex. */ static void __stm_source_link_drop(struct stm_source_device *src, struct stm_device *stm) { struct stm_device *link; + lockdep_assert_held(&stm->link_mutex); + + if (src->data->unlink) + src->data->unlink(src->data); + + /* for stm::link_list modification, we hold both mutex and spinlock */ + spin_lock(&stm->link_lock); spin_lock(&src->link_lock); link = srcu_dereference_check(src->link, &stm_source_srcu, 1); if (WARN_ON_ONCE(link != stm)) { @@ -797,13 +820,13 @@ static void __stm_source_link_drop(struct stm_source_device *src, } stm_output_free(link, &src->output); - /* caller must hold stm::link_lock */ list_del_init(&src->link_entry); /* matches stm_find_device() from stm_source_link_store() */ stm_put_device(link); rcu_assign_pointer(src->link, NULL); spin_unlock(&src->link_lock); + spin_unlock(&stm->link_lock); } /** @@ -825,12 +848,9 @@ static void stm_source_link_drop(struct stm_source_device *src) stm = srcu_dereference(src->link, &stm_source_srcu); if (stm) { - if (src->data->unlink) - src->data->unlink(src->data); - - spin_lock(&stm->link_lock); + mutex_lock(&stm->link_mutex); __stm_source_link_drop(src, stm); - spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); } srcu_read_unlock(&stm_source_srcu, idx); diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h index 95ece0292c99..97ee02241440 100644 --- a/drivers/hwtracing/stm/stm.h +++ b/drivers/hwtracing/stm/stm.h @@ -45,6 +45,7 @@ struct stm_device { int major; unsigned int sw_nmasters; struct stm_data *data; + struct mutex link_mutex; spinlock_t link_lock; struct list_head link_list; /* master allocation */ -- 2.19.1