Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <1db14c3d-6a96-96dd-be76-b81b3a48a2b1@gmail.com>
Date:   Mon, 17 Jan 2022 18:41:04 +0300
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH v16 2/4] dmaengine: tegra: Add tegra gpcdma driver
Content-Language: en-US
To:     Akhil R <akhilrajeev@nvidia.com>,
        "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Krishna Yarlagadda <kyarlagadda@nvidia.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
        "p.zabel@pengutronix.de" <p.zabel@pengutronix.de>,
        Rajesh Gumasta <rgumasta@nvidia.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "thierry.reding@gmail.com" <thierry.reding@gmail.com>,
        "vkoul@kernel.org" <vkoul@kernel.org>
Cc:     Pavan Kunapuli <pkunapuli@nvidia.com>
References: <1641830718-23650-1-git-send-email-akhilrajeev@nvidia.com>
 <1641830718-23650-3-git-send-email-akhilrajeev@nvidia.com>
 <16c73e83-b990-7d8e-ddfd-7cbbe7e407ea@gmail.com>
 <DM5PR12MB1850A5F5ABA9CD5D04C37086C0579@DM5PR12MB1850.namprd12.prod.outlook.com>
From:   Dmitry Osipenko <digetx@gmail.com>
In-Reply-To: <DM5PR12MB1850A5F5ABA9CD5D04C37086C0579@DM5PR12MB1850.namprd12.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

17.01.2022 10:02, Akhil R пишет:
>> 10.01.2022 19:05, Akhil R пишет:
>>> +static int tegra_dma_terminate_all(struct dma_chan *dc)
>>> +{
>>> +     struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
>>> +     unsigned long flags;
>>> +     LIST_HEAD(head);
>>> +     int err;
>>> +
>>> +     if (tdc->dma_desc) {
>>
>> Needs locking protection against racing with the interrupt handler.
> tegra_dma_stop_client() waits for the in-flight transfer 
> to complete and prevents any additional transfer to start. 
> Wouldn't it manage the race? Do you see any potential issue there?

You should consider interrupt handler like a process running in a
parallel thread. The interrupt handler sets tdc->dma_desc to NULL, hence
you'll get NULL dereference in tegra_dma_stop_client().