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=-11.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 5F379C433E0 for ; Sun, 9 Aug 2020 19:01:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29812206A2 for ; Sun, 9 Aug 2020 19:01:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fhcvqaTm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726380AbgHITBm (ORCPT ); Sun, 9 Aug 2020 15:01:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726344AbgHITBl (ORCPT ); Sun, 9 Aug 2020 15:01:41 -0400 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 496AEC061786 for ; Sun, 9 Aug 2020 12:01:41 -0700 (PDT) Received: by mail-pg1-x541.google.com with SMTP id d19so3681367pgl.10 for ; Sun, 09 Aug 2020 12:01:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=dCQmffw/i58ICs4V65P0Gmx0jlfMHsHEylHgWzK3pBQ=; b=fhcvqaTmn2sVgbdLQ8Q30+/nra5OheM++NBD41UQhMjeydwWokLZcZWkFU2vqd8lhd 7z/r0bbwCRJFT1+SjKEfbF9/4pVo6toRdfx+D4Wds03ZIpZwwukif2ngVWtJpZWLFnuM zT1qKc8xQ2QpIc352ypogFc2e6VOU1kBZd5fjbfrg8M8p5+xdvNl/j9xY9PM48Exg1M1 HZTgSpJd7asX5fx1T4fLbZrPWrwBerGIlq7stIsnW5fuXEfz6V5AeA37LVzJBXmtYKq7 M8OOXTKrjmCMjA1/sXDXRbCP+mSf7iZUf/2gYUQ4UhPmyFbWqkLrDNcOhfnpg7BzAA+8 PZAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=dCQmffw/i58ICs4V65P0Gmx0jlfMHsHEylHgWzK3pBQ=; b=DfaDTb8twWLuQBExGaRfVTwwSIPHIzlq/1MzoRqkqeYEy2x9j36l3NzihTrxQuGlfl FIugFUbnoHLY+quy49Xuiv0tzvewaLHVr0JpSry1yAzHaXRrXSbhHhWD36GTpZknFyAa xBb0HeWq56sKgeqRNEeb8ry1UPcrC2RM6GHgeNmR4QmGicgJISEISSKMNEKnOFQDf/8e OSay7gYCQ3p59RiQgBT3jOTV3VsmgRCcdwYKWHxzmeEahhpOn8W8qu0wKaEb9mh0KO1E KvGnIav8O8XnzWZF4/t/ll0yDz0DACqG0gAIcO1w8PJhUnX997DMs+dgoy53pZK2Hy/q D6qA== X-Gm-Message-State: AOAM533oC4eTl9EE3OD4nyVRaMVX44Kz41VguKVNZ1kfzFohyhVGQjbC 7w4eXLOn6noa5XjLXEEF7hQ= X-Google-Smtp-Source: ABdhPJwlLXY+ljlvzCGdp+QZRJzeQ/vj/qHJBv+EBWhmfNMBhXm9UCzuLTPrGe0KTx6Uo3BLidy1uQ== X-Received: by 2002:a63:e747:: with SMTP id j7mr1085881pgk.107.1596999700635; Sun, 09 Aug 2020 12:01:40 -0700 (PDT) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id b13sm18409857pjl.7.2020.08.09.12.01.39 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sun, 09 Aug 2020 12:01:40 -0700 (PDT) Date: Sun, 9 Aug 2020 12:01:38 -0700 From: Guenter Roeck To: Finn Thain Cc: Benjamin Herrenschmidt , Joshua Thompson , Geert Uytterhoeven , linux-m68k@lists.linux-m68k.org, Laurent Vivier , Mark Cave-Ayland , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/9] macintosh/via-macii: Access autopoll_devs when inside lock Message-ID: <20200809190138.GA133890@roeck-us.net> References: <5952dd8a9bc9de90f1acc4790c51dd42b4c98065.1593318192.git.fthain@telegraphics.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5952dd8a9bc9de90f1acc4790c51dd42b4c98065.1593318192.git.fthain@telegraphics.com.au> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-m68k-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi, On Sun, Jun 28, 2020 at 02:23:12PM +1000, Finn Thain wrote: > The interrupt handler should be excluded when accessing the autopoll_devs > variable. > I am quite baffled by this patch. Other than adding an unnecessary lock / unlock sequence, accessing a variable (which is derived from another variable) from inside or outside a lock does not make a difference. If autopoll_devs = devs & 0xfffe is 0 inside the lock, it will just as much be 0 outside the lock, and vice versa. Can you explain this in some more detail ? Not that is matters much since the change already made it into mainline, but I would like to understand what if anything I am missing here. Thanks, Guenter > Fixes: d95fd5fce88f0 ("m68k: Mac II ADB fixes") # v5.0+ > Tested-by: Stan Johnson > Signed-off-by: Finn Thain > --- > drivers/macintosh/via-macii.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/drivers/macintosh/via-macii.c b/drivers/macintosh/via-macii.c > index ac824d7b2dcfc..6aa903529570d 100644 > --- a/drivers/macintosh/via-macii.c > +++ b/drivers/macintosh/via-macii.c > @@ -270,15 +270,12 @@ static int macii_autopoll(int devs) > unsigned long flags; > int err = 0; > > + local_irq_save(flags); > + > /* bit 1 == device 1, and so on. */ > autopoll_devs = devs & 0xFFFE; > > - if (!autopoll_devs) > - return 0; > - > - local_irq_save(flags); > - > - if (current_req == NULL) { > + if (autopoll_devs && !current_req) { > /* Send a Talk Reg 0. The controller will repeatedly transmit > * this as long as it is idle. > */