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=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 EC580C388F7 for ; Fri, 6 Nov 2020 02:18:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E96220756 for ; Fri, 6 Nov 2020 02:18:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604629082; bh=XqYBzQLL2R8K93EL5vhK41zMdWwhehJpa57Qou/yMpQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Mi1NTbuWCYxHG+FmGqu0+b5q4Fh9l0eJagBufTuOknQmo0NRn2yyyXx3/yAx91aQ4 3mBAjCIuJJi9tmazpAsrwEDljWPF+gAk1caOmcLzAqDrXimIJhVGxplczPT7D/N5+E v7smGgO3BnzeRTm3qhGkU+/QXLYokq00woPlmxKI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725900AbgKFCSC (ORCPT ); Thu, 5 Nov 2020 21:18:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:37436 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbgKFCSC (ORCPT ); Thu, 5 Nov 2020 21:18:02 -0500 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 551CC20735; Fri, 6 Nov 2020 02:18:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604629081; bh=XqYBzQLL2R8K93EL5vhK41zMdWwhehJpa57Qou/yMpQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=hdHpEkcMNXKCtuU96tu3ub7OvXqywxAlZMiXLgSEcLIwQh2DZdGSVHUKmzkmQZDYC C08FkDwLniYC4RjGvvlHRHtl5oVct1+N/E5vvS2Y9+ouoaCNUx2qlrv4d1o5ba6RhM hmeurZFiJvYdtDqv6cn6Td+FTBVYamEAJFURb1ws= Date: Fri, 6 Nov 2020 11:17:58 +0900 From: Masami Hiramatsu To: Helge Deller Cc: linux-parisc@vger.kernel.org, James Bottomley , John David Anglin , Steven Rostedt Subject: Re: [PATCH] parisc: ftrace: get_kprobe() must be called with preempt disabled Message-Id: <20201106111758.8b4d6d0197acec6ca4be9a2c@kernel.org> In-Reply-To: <20201103074244.GA5615@ls3530.fritz.box> References: <20201103074244.GA5615@ls3530.fritz.box> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, 3 Nov 2020 08:42:44 +0100 Helge Deller wrote: > As noticed by Masami Hiramatsu, get_kprobe() must be called with preempt > disabled. Doesn't parisc ftrace implementation preempt off? Then it is required. Steve, can we expect that op->func() is called under preempt off always on any arch or is it arch dependent? Thank you, > > Noticed-by: Masami Hiramatsu > Signed-off-by: Helge Deller > > diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c > index 63e3ecb9da81..dd356ad18aca 100644 > --- a/arch/parisc/kernel/ftrace.c > +++ b/arch/parisc/kernel/ftrace.c > @@ -207,13 +212,22 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *ops, struct pt_regs *regs) > { > struct kprobe_ctlblk *kcb; > - struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip); > + struct kprobe *p; > + > + /* > + * We don't want to be preempted for the entire > + * duration of kprobe processing > + */ > + preempt_disable(); > + p = get_kprobe((kprobe_opcode_t *)ip); > > if (unlikely(!p) || kprobe_disabled(p)) > + preempt_enable_no_resched(); > return; > > if (kprobe_running()) { > kprobes_inc_nmissed_count(p); > + preempt_enable_no_resched(); > return; > } > > @@ -235,6 +249,8 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > } > } > __this_cpu_write(current_kprobe, NULL); > + > + preempt_enable_no_resched(); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > -- Masami Hiramatsu