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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 CD2B9C433E1 for ; Fri, 21 Aug 2020 18:39:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96AB720724 for ; Fri, 21 Aug 2020 18:39:23 +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="J2WcNmGW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726624AbgHUSjT (ORCPT ); Fri, 21 Aug 2020 14:39:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725768AbgHUSjM (ORCPT ); Fri, 21 Aug 2020 14:39:12 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B153CC061573; Fri, 21 Aug 2020 11:39:11 -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=qf7iQOKln7FqCs/F0D07PQ4uJRzWTyA3GUp/BaFL3pY=; b=J2WcNmGW4ZaJnH9WyXYj2IWLGP MY9g2ejM9VdCuKeFodacvhJLeWrsYgo8nqefHsNPMU4Vbrin1ug/GspWQXhQ95BueAlwJU5UBVfme xsSe8aV5Fz96VamAaqHdQ1icy5tdze1dzRwTGt4cLmLg4Kr+Xg9qQPIAXAtJYiZxRyPlRWynCDE5p 0qjBdYCKHstNv6qSiYmN1wGDOw4/3X+5ZH2gdOVC3Jp7eb+/miXVMoZwyJWaZJS+e5c/nqkeLwCQi 8+GoU1CglEyEwpGA5NoHefHqEee/kH9Idjl6mMPjdqz8exouGunuAwCseTLazWHRTVt5k6sBsZvrS 5WvpJlVg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k9BwK-0001sV-RA; Fri, 21 Aug 2020 18:39:01 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id E5DB6980DF7; Fri, 21 Aug 2020 20:38:59 +0200 (CEST) Date: Fri, 21 Aug 2020 20:38:59 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Eric Dumazet , Marco Elver , LKML , David Miller , Jakub Kicinski , netdev Subject: Re: [PATCH] random32: Use rcuidle variant for tracepoint Message-ID: <20200821183859.GS3982@worktop.programming.kicks-ass.net> References: <20200821063043.1949509-1-elver@google.com> <20200821085907.GJ1362448@hirez.programming.kicks-ass.net> <20200821113831.340ba051@oasis.local.home> <20200821114141.4b564190@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200821114141.4b564190@oasis.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 21, 2020 at 11:41:41AM -0400, Steven Rostedt wrote: > On Fri, 21 Aug 2020 11:38:31 -0400 > Steven Rostedt wrote: > > > > > At some point we're going to have to introduce noinstr to idle as well. > > > > But until that time this should indeed cure things. > > > > > What the above means, is that ideally we will get rid of all > tracepoints and kasan checks from these RCU not watching locations. But s/and kasan// We only need to get rid of explicit tracepoints -- typically just move them outside of the rcu_idle_enter/exit section. > to do so, we need to move the RCU not watching as close as possible to > where it doesn't need to be watching, and that is not as trivial of a > task as one might think. My recent patch series got a fair way towards that, but yes, there's more work to be done still. > Once we get to a minimal code path for RCU not > to be watching, it will become "noinstr" and tracing and "debugging" > will be disabled in these sections. Right, noinstr is like notrace on steriods, not only does it disallow tracing, it will also disable all the various *SAN/KCOV instrumentation. It also has objtool based validation which ensures noinstr code doesn't call out to regular code.