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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,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 DB166C3A5A2 for ; Tue, 3 Sep 2019 16:37:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B30A62341F for ; Tue, 3 Sep 2019 16:37:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567528636; bh=VhYDu8fEbK18fdi3qDlTweaEVg3p6CaSTXf/vybgIME=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xuPBISyuUexchawrYO1Oj9wqLrgsGW6IICJhr8zVSgg9+Pka/8is1HmTgL1aDKT/t ET63OMaez56eW9KPBCwOQfB2Ulq1+3eEZ7dFNTPwtwYlcexEI1ohrnopWwCeS2JmVy id4ftCvzm5SIVLpNiLEhvaC/EpDm1F28uH7xi+hk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730077AbfICQ0q (ORCPT ); Tue, 3 Sep 2019 12:26:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:47792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730177AbfICQ0p (ORCPT ); Tue, 3 Sep 2019 12:26:45 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 29A0E238C5; Tue, 3 Sep 2019 16:26:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567528004; bh=VhYDu8fEbK18fdi3qDlTweaEVg3p6CaSTXf/vybgIME=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PjVdcUApmjeGC0xzLSCpOM5LuD+iHYAaxoMhQyXlvZ0JcHTfxjxlDBQvnMDFpL7TZ Q7Dv5Ioko/MkcttnY3MgdVvqdR8AYpM0VSyAvlQlcKgr3H55AYy9OtIQ9JZNtkVBp0 VlQdmaByo0yMRvAFFhT9eWJNRiMBisKI20AMyXkc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vineet Gupta , Sasha Levin , linux-snps-arc@lists.infradead.org Subject: [PATCH AUTOSEL 4.19 049/167] ARC: show_regs: lockdep: re-enable preemption Date: Tue, 3 Sep 2019 12:23:21 -0400 Message-Id: <20190903162519.7136-49-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190903162519.7136-1-sashal@kernel.org> References: <20190903162519.7136-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vineet Gupta [ Upstream commit f731a8e89f8c78985707c626680f3e24c7a60772 ] signal handling core calls show_regs() with preemption disabled which on ARC takes mmap_sem for mm/vma access, causing lockdep splat. | [ARCLinux]# ./segv-null-ptr | potentially unexpected fatal signal 11. | BUG: sleeping function called from invalid context at kernel/fork.c:1011 | in_atomic(): 1, irqs_disabled(): 0, pid: 70, name: segv-null-ptr | no locks held by segv-null-ptr/70. | CPU: 0 PID: 70 Comm: segv-null-ptr Not tainted 4.18.0+ #69 | | Stack Trace: | arc_unwind_core+0xcc/0x100 | ___might_sleep+0x17a/0x190 | mmput+0x16/0xb8 | show_regs+0x52/0x310 | get_signal+0x5ee/0x610 | do_signal+0x2c/0x218 | resume_user_mode_begin+0x90/0xd8 Workaround by re-enabling preemption temporarily. Note that the preemption disabling in core code around show_regs() was introduced by commit 3a9f84d354ce ("signals, debug: fix BUG: using smp_processor_id() in preemptible code in print_fatal_signal()") to silence a differnt lockdep seen on x86 bakc in 2009. Cc: Signed-off-by: Vineet Gupta Signed-off-by: Sasha Levin --- arch/arc/kernel/troubleshoot.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c index 5c6663321e873..215f515442e03 100644 --- a/arch/arc/kernel/troubleshoot.c +++ b/arch/arc/kernel/troubleshoot.c @@ -179,6 +179,12 @@ void show_regs(struct pt_regs *regs) struct task_struct *tsk = current; struct callee_regs *cregs; + /* + * generic code calls us with preemption disabled, but some calls + * here could sleep, so re-enable to avoid lockdep splat + */ + preempt_enable(); + print_task_path_n_nm(tsk); show_regs_print_info(KERN_INFO); @@ -221,6 +227,8 @@ void show_regs(struct pt_regs *regs) cregs = (struct callee_regs *)current->thread.callee_reg; if (cregs) show_callee_regs(cregs); + + preempt_disable(); } void show_kernel_fault_diag(const char *str, struct pt_regs *regs, -- 2.20.1