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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 A989AC433E2 for ; Fri, 28 Aug 2020 15:18:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A72220757 for ; Fri, 28 Aug 2020 15:18:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="akxcjAXj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728329AbgH1PSy (ORCPT ); Fri, 28 Aug 2020 11:18:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726219AbgH1PSi (ORCPT ); Fri, 28 Aug 2020 11:18:38 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 497A4C061232; Fri, 28 Aug 2020 08:18:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JKeQhoL4ZGEC1cQ3dqsE2L0OJR8mxSbszUgCFLGMeHU=; b=akxcjAXj7YDrUyYX/ul5o0ob5U 1i5uGkMZRpQ5UtXXOws2Aba+T8Q+HX0Y8z4nA/7EkMhIL1pW9f22OIg9Bld1yw5lexb4ubdOtr8jk SDLi3SwWww7gVfAW+35tZgteI7vlPuuiNX0EuvxBBSaZ4F3OdCxw2j7gsW/WqjQbeYegHB71HNvj6 TtBUBJUtkFETb8dInAatRAxKIqT7RjQ05Ww9A4V8zHT9XZsknYq+FYy4JH6qu3K6vKIlDxaSDfanq KumAjmhx4ZsB06vkUnJJ9keX87zp4QGtiyfNn5dlPLQkDgjva9CtqZAxhzoKWhAV5AcCkbZ7M079h N83qcvtg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kBg8m-0003cX-Cf; Fri, 28 Aug 2020 15:18:08 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 85D5A30015A; Fri, 28 Aug 2020 17:18:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 353B42C5FEF21; Fri, 28 Aug 2020 17:18:06 +0200 (CEST) Date: Fri, 28 Aug 2020 17:18:06 +0200 From: peterz@infradead.org To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com, x86@kernel.org, davem@davemloft.net, rostedt@goodmis.org, naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, linux-arch@vger.kernel.org, cameron@moodycamel.com, oleg@redhat.com, will@kernel.org, paulmck@kernel.org Subject: Re: [PATCH v4 20/23] [RFC] kprobes: Remove task scan for updating kretprobe_instance Message-ID: <20200828151806.GF1362448@hirez.programming.kicks-ass.net> References: <159861759775.992023.12553306821235086809.stgit@devnote2> <159861781740.992023.4956784710984854658.stgit@devnote2> <20200828125236.GA1362448@hirez.programming.kicks-ass.net> <20200829001010.7ec1a183c2294f7bd843b153@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200829001010.7ec1a183c2294f7bd843b153@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 29, 2020 at 12:10:10AM +0900, Masami Hiramatsu wrote: > On Fri, 28 Aug 2020 14:52:36 +0200 > peterz@infradead.org wrote: > > > synchronize_rcu(); > > > > This one might help, this means we can do rcu_read_lock() around > > get_kretprobe() and it's usage. Can we call rp->handler() under RCU? > > Yes, as I said above, the get_kretprobe() (and kretprobe handler) must be > called under preempt-disabled. Then we don't need the ordering; we'll need READ_ONCE() (or rcu_derefernce()) to make sure the address dependency works on Alpha. And a comment/assertion that explains this might not go amiss in get_kretprobe().