Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752967AbaLAJhk (ORCPT ); Mon, 1 Dec 2014 04:37:40 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:50811 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752733AbaLAJhi (ORCPT ); Mon, 1 Dec 2014 04:37:38 -0500 Message-ID: <547C36DB.7060903@hitachi.com> Date: Mon, 01 Dec 2014 18:37:31 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Steve Capper Cc: David Long , "Jon Medhurst (Tixy)" , Russell King , Ananth N Mavinakayanahalli , Sandeepa Prabhu , Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" , Anil S Keshavamurthy , William Cohen , David Miller , "linux-arm-kernel@lists.infradead.org" Subject: Re: Re: Re: [PATCH v3 0/5] ARM64: Add kernel probes(Kprobes) support References: <1416292375-29560-1-git-send-email-dave.long@linaro.org> <20141120135851.GA32528@linaro.org> <54759041.9080105@hitachi.com> <20141126100325.GA9157@linaro.org> <5476120D.9030703@linaro.org> <5476BFB4.2020705@hitachi.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/11/29 1:01), Steve Capper wrote: > On 27 November 2014 at 06:07, Masami Hiramatsu > wrote: >> (2014/11/27 3:59), Steve Capper wrote: >>> The crash is extremely easy to reproduce. >>> >>> I've not observed any missed events on a kprobe on an arm64 system >>> that's still alive. >>> My (limited!) understanding is that this suggests there could be a >>> problem with how missed events from a recursive call to memcpy are >>> being handled. >> >> I think so too. BTW, could you bisect that? :) >> > > I can't bisect, but the following functions look suspicious to me > (again I'm new to kprobes...): > kprobes_save_local_irqflag > kprobes_restore_local_irqflag > > I think these are breaking somehow when nested (i.e. from a recursive probe). Agreed. On x86, prev_kprobe has old_flags and saved_flags, this at least must have saved_irqflag and save/restore it in save/restore_previous_kprobe(). What about adding this? struct prev_kprobe { struct kprobe *kp; unsigned int status; + unsigned long saved_irqflag; }; and static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; + kcb->prev_kprobe.saved_irqflag = kcb->saved_irqflag; } static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->saved_irqflag = kcb->prev_kprobe.saved_irqflag; } > That would explain why the state of play of the interrupts is in an > unexpected state in the crash I reported: > "The point of failure in the panic was: > fs/buffer.c:1257 > > static inline void check_irqs_on(void) > { > #ifdef irqs_disabled > BUG_ON(irqs_disabled()); > #endif > } > " > > This is all new to me so I'm still at the head-scratching stage. Ah, I see. Thank you, > > David, > Does the above make sense to you? Have you managed to reproduce the crash I get? > > Cheers, > -- > Steve > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/