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,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 C7A91C43381 for ; Mon, 4 Mar 2019 08:29:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AE1D21019 for ; Mon, 4 Mar 2019 08:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688149; bh=iQOumdJ5rwgVbtb4uvWYYVnN11Ts/7Yc0/EeZIKBxmg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MwUp7vtivmRnkcdeUKDqZ2tDMFuPljcC04X5gc5MSdGzKaWulR35/tR1D+ky3izfh InbfU3aHN76x8L35ABgguVxJOQjgUSpGR+4QHFtyduS0zmU8PEHN5VL2+OKxcYXHN3 EiPoLEWB84HyA/Ofhae2sy98GvV9ySSVMZBw/mdo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727508AbfCDI3I (ORCPT ); Mon, 4 Mar 2019 03:29:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:55086 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727500AbfCDI3F (ORCPT ); Mon, 4 Mar 2019 03:29:05 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 BBEAD20823; Mon, 4 Mar 2019 08:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688144; bh=iQOumdJ5rwgVbtb4uvWYYVnN11Ts/7Yc0/EeZIKBxmg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MRCKHYMMvHa9XqxLkR4sgk9OoiYkYRRQJe2+2XWnbp8t89a2SXi3RDcG53a59T8K0 JvD1odh4e0VWkF5Up7HcXhp0V1mW90cSZ6vXjJc1e4//RW5JMLww/S4GuxBS+oND0O QKj1onoUXYrAKhambYhW6Ds/EEjyB6RhS1cKjyIA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, William Kucharski , Vineet Gupta , Sasha Levin Subject: [PATCH 4.19 31/78] ARC: show_regs: lockdep: avoid page allocator... Date: Mon, 4 Mar 2019 09:22:14 +0100 Message-Id: <20190304081626.898855953@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190304081625.508788074@linuxfoundation.org> References: <20190304081625.508788074@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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit ab6c03676cb190156603cf4c5ecf97aa406c9c53 ] and use smaller/on-stack buffer instead The motivation for this change was lockdep splat like below. | potentially unexpected fatal signal 11. | BUG: sleeping function called from invalid context at ../mm/page_alloc.c:4317 | in_atomic(): 1, irqs_disabled(): 0, pid: 57, name: segv | no locks held by segv/57. | Preemption disabled at: | [<8182f17e>] get_signal+0x4a6/0x7c4 | CPU: 0 PID: 57 Comm: segv Not tainted 4.17.0+ #23 | | Stack Trace: | arc_unwind_core.constprop.1+0xd0/0xf4 | __might_sleep+0x1f6/0x234 | __get_free_pages+0x174/0xca0 | show_regs+0x22/0x330 | get_signal+0x4ac/0x7c4 # print_fatal_signals() -> preempt_disable() | do_signal+0x30/0x224 | resume_user_mode_begin+0x90/0xd8 So signal handling core calls show_regs() with preemption disabled but an ensuing GFP_KERNEL page allocator call is flagged by lockdep. We could have switched to GFP_NOWAIT, but turns out that is not enough anways and eliding page allocator call leads to less code and instruction traces to sift thru when debugging pesky crashes. FWIW, this patch doesn't cure the lockdep splat (which next patch does). Reviewed-by: William Kucharski Signed-off-by: Vineet Gupta Signed-off-by: Sasha Levin --- arch/arc/kernel/troubleshoot.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-) diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c index e8d9fb4523462..5c6663321e873 100644 --- a/arch/arc/kernel/troubleshoot.c +++ b/arch/arc/kernel/troubleshoot.c @@ -18,6 +18,8 @@ #include #include +#define ARC_PATH_MAX 256 + /* * Common routine to print scratch regs (r0-r12) or callee regs (r13-r25) * -Prints 3 regs per line and a CR. @@ -58,11 +60,12 @@ static void show_callee_regs(struct callee_regs *cregs) print_reg_file(&(cregs->r13), 13); } -static void print_task_path_n_nm(struct task_struct *tsk, char *buf) +static void print_task_path_n_nm(struct task_struct *tsk) { char *path_nm = NULL; struct mm_struct *mm; struct file *exe_file; + char buf[ARC_PATH_MAX]; mm = get_task_mm(tsk); if (!mm) @@ -72,7 +75,7 @@ static void print_task_path_n_nm(struct task_struct *tsk, char *buf) mmput(mm); if (exe_file) { - path_nm = file_path(exe_file, buf, 255); + path_nm = file_path(exe_file, buf, ARC_PATH_MAX-1); fput(exe_file); } @@ -80,10 +83,9 @@ static void print_task_path_n_nm(struct task_struct *tsk, char *buf) pr_info("Path: %s\n", !IS_ERR(path_nm) ? path_nm : "?"); } -static void show_faulting_vma(unsigned long address, char *buf) +static void show_faulting_vma(unsigned long address) { struct vm_area_struct *vma; - char *nm = buf; struct mm_struct *active_mm = current->active_mm; /* can't use print_vma_addr() yet as it doesn't check for @@ -96,8 +98,11 @@ static void show_faulting_vma(unsigned long address, char *buf) * if the container VMA is not found */ if (vma && (vma->vm_start <= address)) { + char buf[ARC_PATH_MAX]; + char *nm = "?"; + if (vma->vm_file) { - nm = file_path(vma->vm_file, buf, PAGE_SIZE - 1); + nm = file_path(vma->vm_file, buf, ARC_PATH_MAX-1); if (IS_ERR(nm)) nm = "?"; } @@ -173,13 +178,8 @@ void show_regs(struct pt_regs *regs) { struct task_struct *tsk = current; struct callee_regs *cregs; - char *buf; - buf = (char *)__get_free_page(GFP_KERNEL); - if (!buf) - return; - - print_task_path_n_nm(tsk, buf); + print_task_path_n_nm(tsk); show_regs_print_info(KERN_INFO); show_ecr_verbose(regs); @@ -189,7 +189,7 @@ void show_regs(struct pt_regs *regs) (void *)regs->blink, (void *)regs->ret); if (user_mode(regs)) - show_faulting_vma(regs->ret, buf); /* faulting code, not data */ + show_faulting_vma(regs->ret); /* faulting code, not data */ pr_info("[STAT32]: 0x%08lx", regs->status32); @@ -221,8 +221,6 @@ void show_regs(struct pt_regs *regs) cregs = (struct callee_regs *)current->thread.callee_reg; if (cregs) show_callee_regs(cregs); - - free_page((unsigned long)buf); } void show_kernel_fault_diag(const char *str, struct pt_regs *regs, -- 2.19.1