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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 F099CC35242 for ; Tue, 11 Feb 2020 03:50:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE214206D7 for ; Tue, 11 Feb 2020 03:50:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="NL+ktiBP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727857AbgBKDua (ORCPT ); Mon, 10 Feb 2020 22:50:30 -0500 Received: from mail-pf1-f193.google.com ([209.85.210.193]:38077 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727850AbgBKDua (ORCPT ); Mon, 10 Feb 2020 22:50:30 -0500 Received: by mail-pf1-f193.google.com with SMTP id x185so4769364pfc.5 for ; Mon, 10 Feb 2020 19:50:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=F0U52WoOTmznpmVQlips03nRcDHW124eA6wJkCew2vE=; b=NL+ktiBPYYZ8zpXButlfJWwqcrHceS7f+3rgqCXGxa4b1J9sQcm+Izzs3jSMbuLvXS wmZgfKzkymB752daqLQRXYSSjmjcQfqTQrQArmhNuSj0WYHexB1zhHZLDkXM6M8Zbb7u sRy+i6OXluZ43OTQb2U6TD6FMmvXPMQ0LVEwOJMJRRttU4yMnU8PxWoXIP6Zty0EcqU3 QdM13bpXtf0j9aYF4TilBLL8yolnqqpzRrkwUGTeP5EKUW1JROJDxM64aPrOV7ABl3kd yAdZ3WIeMLEoFeLEGUNBkb24Lq/S1gR1oDNwrIoT1eYh40wdI5STHbWhedsJ9tQ7kRXT FmLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=F0U52WoOTmznpmVQlips03nRcDHW124eA6wJkCew2vE=; b=dWNv09vbdmsqBFHvRQC/nqbW0KC/jRw5gwkNYqT87/NMb9Mdkr5iBNlG2hiadnX87L 8v/ycDKyYj8lrZA2HuiH+K3HeDiCetB5/bdwqrw+M3ElR1NUB7+7ePcxpuVBMx2g04Sb xs2MgsU29AJdoilHqWIK1MBzr+PTpO2UHeCsnGsV+Zfr8jH6HGs6Vb8u/J5HGu4Fx168 TdpAEo2TO8d+sVAkX8N6xl/vpeN+CkV6XDUnz82d8QXROMgTNB8rpiTUAT+GSXHszM3e /DzQ0j0wDjU98Dp1gT3drGOyEjOcjGuD+D9i9DTZZJMXZB/ZYZqXbhUcVyoJzWuJIg7t Ot6w== X-Gm-Message-State: APjAAAX5PHFWnsXLc1kXvc8nzTD0JF7h9QPY/iguS1BGEGClF91646ZW EVy1Lg+bUS5f2pVlkjb+NHmp X-Google-Smtp-Source: APXvYqzKmjTxhZKI1zpyKOREnV/LDVQAEKBbMyHrXGkxmtbsTL98gQk3MjS2BVFjI386gOomzrBYAg== X-Received: by 2002:aa7:9218:: with SMTP id 24mr1188856pfo.145.1581393029174; Mon, 10 Feb 2020 19:50:29 -0800 (PST) Received: from Mani-XPS-13-9360 ([2409:4072:638b:7653:754d:196d:c455:1f88]) by smtp.gmail.com with ESMTPSA id e16sm1513040pgk.77.2020.02.10.19.50.22 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Feb 2020 19:50:28 -0800 (PST) Date: Tue, 11 Feb 2020 09:20:20 +0530 From: Manivannan Sadhasivam To: Chris Lew Cc: Jakub Kicinski , gregkh@linuxfoundation.org, arnd@arndb.de, smohanad@codeaurora.org, jhugo@codeaurora.org, kvalo@codeaurora.org, bjorn.andersson@linaro.org, hemantk@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, "David S. Miller" , netdev@vger.kernel.org Subject: Re: [PATCH v2 14/16] net: qrtr: Add MHI transport layer Message-ID: <20200211035020.GA3358@Mani-XPS-13-9360> References: <20200131135009.31477-1-manivannan.sadhasivam@linaro.org> <20200131135009.31477-15-manivannan.sadhasivam@linaro.org> <20200203101225.43bd27bc@cakuba.hsd1.ca.comcast.net> <20200204081914.GB7452@Mani-XPS-13-9360> <53018abf-4bc9-1ddb-0be5-a9a3b9871a33@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53018abf-4bc9-1ddb-0be5-a9a3b9871a33@codeaurora.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi Chris, On Thu, Feb 06, 2020 at 04:14:19PM -0800, Chris Lew wrote: > > On 2/4/2020 12:19 AM, Manivannan Sadhasivam wrote: > > Hi Jakub, > > > > On Mon, Feb 03, 2020 at 10:12:25AM -0800, Jakub Kicinski wrote: > > > On Fri, 31 Jan 2020 19:20:07 +0530, Manivannan Sadhasivam wrote: > > > > +/* From QRTR to MHI */ > > > > +static void qcom_mhi_qrtr_ul_callback(struct mhi_device *mhi_dev, > > > > + struct mhi_result *mhi_res) > > > > +{ > > > > + struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev); > > > > + struct qrtr_mhi_pkt *pkt; > > > > + unsigned long flags; > > > > + > > > > + spin_lock_irqsave(&qdev->ul_lock, flags); > > > > + pkt = list_first_entry(&qdev->ul_pkts, struct qrtr_mhi_pkt, node); > > > > + list_del(&pkt->node); > > > > + complete_all(&pkt->done); > > > > + > > > > + kref_put(&pkt->refcount, qrtr_mhi_pkt_release); > > > Which kref_get() does this pair with? > > > > > > Looks like qcom_mhi_qrtr_send() will release a reference after > > > completion, too. > > > > > Yikes, there is some issue here... > > > > Acutally the issue is not in what you referred above but the overall kref > > handling itself. Please see below. > > > > kref_put() should be present in qcom_mhi_qrtr_ul_callback() as it will > > decrement the refcount which got incremented in qcom_mhi_qrtr_send(). It > > should be noted that kref_init() will fix the refcount to 1 and kref_get() will > > increment to 2. So for properly releasing the refcount to 0, we need to call > > kref_put() twice. > > > > So if all goes well, the refcount will get decremented twice in > > qcom_mhi_qrtr_ul_callback() as well as in qcom_mhi_qrtr_send() and we are good. > > > > But, if the transfer has failed ie., when qcom_mhi_qrtr_ul_callback() doesn't > > get called, then we are leaking the refcount. I need to rework the kref handling > > code in next iteration. > > > > Thanks for triggering this! > > > > Regards, > > Mani > > > > > > + spin_unlock_irqrestore(&qdev->ul_lock, flags); > > > > +} > > Hi Mani, > > I'm not sure if this was changed in your patches but MHI is supposed to give a > ul_callback() for any packet that is successfully queued. In the case of the > transfer failing, the ul_callback() should still be called so there should > be no refcount leaking. It is an essential assumption I made, if that no longer > holds true then the entire driver needs to be reworked. > Your assumption is correct. Only when the packet gets queued into the transfer ring, the ul_xfer_cb will be called irrespective of the transfer state (success or failure). But when the mhi_queue_transfer() returns even before queuing any packet, then we need to decrease the refcount in the error path. Please correct me if I'm wrong. Thanks, Mani > Thanks, > Chris > > -- > > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project