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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 1B0EFC282CE for ; Wed, 24 Apr 2019 08:56:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF7B9218FC for ; Wed, 24 Apr 2019 08:56:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729562AbfDXI4M (ORCPT ); Wed, 24 Apr 2019 04:56:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:40134 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728580AbfDXI4G (ORCPT ); Wed, 24 Apr 2019 04:56:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 713A5AED7; Wed, 24 Apr 2019 08:56:05 +0000 (UTC) From: Petr Mladek To: Jiri Kosina , Josh Poimboeuf , Miroslav Benes Cc: Joe Lawrence , Kamalesh Babulal , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH 3/3] livepatch: Cleanup message handling in klp_try_switch_task() Date: Wed, 24 Apr 2019 10:55:50 +0200 Message-Id: <20190424085550.29612-4-pmladek@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190424085550.29612-1-pmladek@suse.com> References: <20190424085550.29612-1-pmladek@suse.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org WARN_ON_ONCE() could not be called safely under rq lock because of console deadlock issues. Fortunately, simple printk_deferred() is enough because the warning is printed from a well defined location and context. Also klp_try_switch_task() is called under klp_mutex. Therefore, the buffer for debug messages could be static. Signed-off-by: Petr Mladek --- kernel/livepatch/transition.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c index 9c89ae8b337a..e8183d18227f 100644 --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c @@ -254,6 +254,7 @@ static int klp_check_stack_func(struct klp_func *func, static int klp_check_stack(struct task_struct *task, char *err_buf) { static unsigned long entries[MAX_STACK_ENTRIES]; + static int enosys_warned; struct stack_trace trace; struct klp_object *obj; struct klp_func *func; @@ -263,8 +264,16 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) trace.nr_entries = 0; trace.max_entries = MAX_STACK_ENTRIES; trace.entries = entries; + ret = save_stack_trace_tsk_reliable(task, &trace); - WARN_ON_ONCE(ret == -ENOSYS); + if (ret == -ENOSYS) { + if (!enosys_warned) { + printk_deferred(KERN_WARNING "%s: save_stack_trace_tsk_reliable() not supported on this architecture.\n", + __func__); + enosys_warned = 1; + } + return ret; + } if (ret) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d has an unreliable stack\n", @@ -297,11 +306,11 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) */ static bool klp_try_switch_task(struct task_struct *task) { + static char err_buf[STACK_ERR_BUF_SIZE]; struct rq *rq; struct rq_flags flags; int ret; bool success = false; - char err_buf[STACK_ERR_BUF_SIZE]; err_buf[0] = '\0'; @@ -336,15 +345,15 @@ static bool klp_try_switch_task(struct task_struct *task) task_rq_unlock(rq, task, &flags); /* - * Due to console deadlock issues, pr_debug() can't be used while - * holding the task rq lock. Instead we have to use a temporary buffer + * printk_deferred() need to be used under rq lock to avoid + * console deadlock issues. But it does not support the dynamic + * debug feature. Instead we have to use a temporary buffer * and print the debug message after releasing the lock. */ if (err_buf[0] != '\0') pr_debug("%s", err_buf); return success; - } /* -- 2.16.4