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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 14C0AC6786F for ; Tue, 30 Oct 2018 12:10:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1E9720831 for ; Tue, 30 Oct 2018 12:10:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="s7ZAakij" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1E9720831 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lunn.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728032AbeJ3VDy (ORCPT ); Tue, 30 Oct 2018 17:03:54 -0400 Received: from vps0.lunn.ch ([185.16.172.187]:46056 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727863AbeJ3VDy (ORCPT ); Tue, 30 Oct 2018 17:03:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date; bh=DA0W34KdCdXK/M1/fLBkxMH1gHDRPC+AUNQWiO2+iN0=; b=s7ZAakijiwU/THh9P3rH0x0//N+a8O59YT1lpdqG/Y7to0auMvCnFbIvLiabkYjg0gTQj0PO2Tw6G5J31dHRbk+w1y/uSuhRpHYQxUP9peFSAXJOlzeEG/nPy0QKE2RCJiNlmvc/MZM6kpUY5S0Ua/CvUvfaDDtSueMWX7kZbfA=; Received: from andrew by vps0.lunn.ch with local (Exim 4.84_2) (envelope-from ) id 1gHSqs-0007U1-3i; Tue, 30 Oct 2018 13:10:30 +0100 Date: Tue, 30 Oct 2018 13:10:30 +0100 From: Andrew Lunn To: Kurt Kanzenbach Cc: Anirudha Sarangi , John Linn , "David S. Miller" , Michal Simek , Radhey Shyam Pandey , YueHaibing , netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] net: xilinx_emaclite: recheck condition after timeout in mdio_wait() Message-ID: <20181030121030.GD27873@lunn.ch> References: <20181030093139.10226-1-kurt@linutronix.de> <20181030093139.10226-3-kurt@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181030093139.10226-3-kurt@linutronix.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 30, 2018 at 10:31:39AM +0100, Kurt Kanzenbach wrote: > The function could report a false positive if it gets preempted between reading > the XEL_MDIOCTRL_OFFSET register and checking for the timeout. In such a case, > the condition has to be rechecked to avoid false positives. > > Therefore, check for expected condition even after the timeout occurred. > > Signed-off-by: Kurt Kanzenbach > --- > drivers/net/ethernet/xilinx/xilinx_emaclite.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c b/drivers/net/ethernet/xilinx/xilinx_emaclite.c > index 639e3e99af46..957d03085bd0 100644 > --- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c > +++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c > @@ -714,19 +714,29 @@ static irqreturn_t xemaclite_interrupt(int irq, void *dev_id) > static int xemaclite_mdio_wait(struct net_local *lp) > { > unsigned long end = jiffies + 2; > + u32 val; > > /* wait for the MDIO interface to not be busy or timeout > * after some time. > */ > - while (xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET) & > - XEL_MDIOCTRL_MDIOSTS_MASK) { > + while (1) { > + val = xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET); Hi Kurt It looks like readx_poll_timeout() should work here. Andrew From mboxrd@z Thu Jan 1 00:00:00 1970 From: andrew@lunn.ch (Andrew Lunn) Date: Tue, 30 Oct 2018 13:10:30 +0100 Subject: [PATCH 2/2] net: xilinx_emaclite: recheck condition after timeout in mdio_wait() In-Reply-To: <20181030093139.10226-3-kurt@linutronix.de> References: <20181030093139.10226-1-kurt@linutronix.de> <20181030093139.10226-3-kurt@linutronix.de> Message-ID: <20181030121030.GD27873@lunn.ch> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Oct 30, 2018 at 10:31:39AM +0100, Kurt Kanzenbach wrote: > The function could report a false positive if it gets preempted between reading > the XEL_MDIOCTRL_OFFSET register and checking for the timeout. In such a case, > the condition has to be rechecked to avoid false positives. > > Therefore, check for expected condition even after the timeout occurred. > > Signed-off-by: Kurt Kanzenbach > --- > drivers/net/ethernet/xilinx/xilinx_emaclite.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c b/drivers/net/ethernet/xilinx/xilinx_emaclite.c > index 639e3e99af46..957d03085bd0 100644 > --- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c > +++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c > @@ -714,19 +714,29 @@ static irqreturn_t xemaclite_interrupt(int irq, void *dev_id) > static int xemaclite_mdio_wait(struct net_local *lp) > { > unsigned long end = jiffies + 2; > + u32 val; > > /* wait for the MDIO interface to not be busy or timeout > * after some time. > */ > - while (xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET) & > - XEL_MDIOCTRL_MDIOSTS_MASK) { > + while (1) { > + val = xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET); Hi Kurt It looks like readx_poll_timeout() should work here. Andrew