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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 81888C433FE for ; Mon, 7 Dec 2020 22:47:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51ADF239E4 for ; Mon, 7 Dec 2020 22:47:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727550AbgLGWrb (ORCPT ); Mon, 7 Dec 2020 17:47:31 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:39396 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726069AbgLGWrb (ORCPT ); Mon, 7 Dec 2020 17:47:31 -0500 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1607381209; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=DF7s5pk4Zw7F4Z2nppe0ZuFvyidXGsr6pkOHRZYg040=; b=z6h2Skd6Npw6+UOW47F4wiFBtAPxZNXBfKkjPDYXIY+em1Iu2EMMtdlgJLp7nq3MeQzG8h oFy82ZG6DqhcJ0rM6YSXZhSdU9a71vzi2Ure7bmyfXdSTcjVKxczPBqNAkwpA7LzUfuIYj Xk+SzGF56zatuASCFWXgzX/MShBS3Gcykho5iu91a+Z6A5hAIF70N6VsPW15PCY5xSMh20 r67/fp2pdSG0ZXaGCniMWypCTCsCB92q+003FtxmjZsVwa4/DbdJMAC7EaAXsN6rj9zUmG XkCEeTlCLiGhO9Xf8uf4I9v1TlZ5RAbFzjExcVQDasbU+HMt/4qlw0W1beTuEg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1607381209; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=DF7s5pk4Zw7F4Z2nppe0ZuFvyidXGsr6pkOHRZYg040=; b=CeWqBvqQZSg4eFg2hQfpVHwHizWRr6ZhqODicAjGwNBL3A0aqsxbjIyBNu8+zte/q6gaBW frVmiJRylI/MBICA== To: paulmck@kernel.org Cc: Marco Elver , Peter Zijlstra , LKML , kasan-dev , Ingo Molnar , Frederic Weisbecker , Will Deacon , Naresh Kamboju , syzbot+23a256029191772c2f02@syzkaller.appspotmail.com, syzbot+56078ac0b9071335a745@syzkaller.appspotmail.com, syzbot+867130cb240c41f15164@syzkaller.appspotmail.com Subject: Re: [patch 3/3] tick: Annotate tick_do_timer_cpu data races In-Reply-To: <20201207223853.GL2657@paulmck-ThinkPad-P72> References: <20201206211253.919834182@linutronix.de> <20201206212002.876987748@linutronix.de> <20201207120943.GS3021@hirez.programming.kicks-ass.net> <87y2i94igo.fsf@nanos.tec.linutronix.de> <20201207194406.GK2657@paulmck-ThinkPad-P72> <87blf547d2.fsf@nanos.tec.linutronix.de> <20201207223853.GL2657@paulmck-ThinkPad-P72> Date: Mon, 07 Dec 2020 23:46:48 +0100 Message-ID: <878sa944kn.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 07 2020 at 14:38, Paul E. McKenney wrote: > On Mon, Dec 07, 2020 at 10:46:33PM +0100, Thomas Gleixner wrote: >> On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote: >> > On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote: >> >> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote: >> >> I currently don't know what the rule for Peter's preferred variant >> >> would be, without running the risk of some accidentally data_race()'d >> >> accesses. >> >> >> >> Thoughts? >> > >> > I am also concerned about inadvertently covering code with data_race(). >> > >> > Also, in this particular case, why data_race() rather than READ_ONCE()? >> > Do we really expect the compiler to be able to optimize this case >> > significantly without READ_ONCE()? >> >> That was your suggestion a week or so ago :) > > You expected my suggestion to change? ;-) Your suggestion was data_race() IIRC but I might have lost track in that conversation.