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=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 9A20EC10F03 for ; Mon, 4 Mar 2019 08:40:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DD1C20823 for ; Mon, 4 Mar 2019 08:40:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688805; bh=G7OLDbRbN2Dgbc6y9SsgXqXL0PgvgidTjN/TGYJD5ik=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=QQdiQ6VFO0zSR5e81MCM2e7eWTgoW5wqFdbPRekM+CIzaIVDaCj37NgvTzj8mo+lQ xGrsEC+7ZLXjl5ONfpNKmE5PhiIwrLC3qmD4FrPWEB/xFGZdkdgsddErassdoIsJK2 S7637pmPgfrpu5d0He7a4bJ+DQBL2+YEmpIIq51A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726938AbfCDIdS (ORCPT ); Mon, 4 Mar 2019 03:33:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:37694 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727105AbfCDIdR (ORCPT ); Mon, 4 Mar 2019 03:33:17 -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 0C59B20823; Mon, 4 Mar 2019 08:33:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551688395; bh=G7OLDbRbN2Dgbc6y9SsgXqXL0PgvgidTjN/TGYJD5ik=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XOy9FUvS89wORN12qqgPu9VZ7hoUuzlCGuPKQbxFpu6Z8tFDgSrof3V+gP/84aCjH nORaSd7CoQbO8gja8nTvS3DjyhVbH8wJn2iPkKN3vX8cNfFSWS+yhqB/0lejSH1YsF XHFSM3lY8TT9+5qj60K3Po1silLAeI1apAgX8bB4= 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 4.20 31/88] ARC: show_regs: lockdep: avoid page allocator... Date: Mon, 4 Mar 2019 09:22:14 +0100 Message-Id: <20190304081631.830535059@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190304081630.610632175@linuxfoundation.org> References: <20190304081630.610632175@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 4.20-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