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[79.139.233.37]) by smtp.googlemail.com with ESMTPSA id p15sm1186393lfo.88.2020.01.29.06.39.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Jan 2020 06:39:08 -0800 (PST) Subject: Re: [PATCH v5 05/14] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list To: Jon Hunter , Laxman Dewangan , Vinod Koul , Dan Williams , Thierry Reding , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Cc: dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200123230325.3037-1-digetx@gmail.com> <20200123230325.3037-6-digetx@gmail.com> From: Dmitry Osipenko Message-ID: <5f867023-d49a-aff5-8d7f-d682a3b32770@gmail.com> Date: Wed, 29 Jan 2020 17:39:07 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 29.01.2020 14:01, Jon Hunter пишет: > > On 23/01/2020 23:03, Dmitry Osipenko wrote: >> The interrupt handler puts a half-completed DMA descriptor on a free list >> and then schedules tasklet to process bottom half of the descriptor that >> executes client's callback, this creates possibility to pick up the busy >> descriptor from the free list. Thus let's disallow descriptor's re-use >> until it is fully processed. >> >> Acked-by: Jon Hunter >> Signed-off-by: Dmitry Osipenko >> --- >> drivers/dma/tegra20-apb-dma.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c >> index 1b8a11804962..aafad50d075e 100644 >> --- a/drivers/dma/tegra20-apb-dma.c >> +++ b/drivers/dma/tegra20-apb-dma.c >> @@ -281,7 +281,7 @@ static struct tegra_dma_desc *tegra_dma_desc_get( >> >> /* Do not allocate if desc are waiting for ack */ >> list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) { >> - if (async_tx_test_ack(&dma_desc->txd)) { >> + if (async_tx_test_ack(&dma_desc->txd) && !dma_desc->cb_count) { >> list_del(&dma_desc->node); >> spin_unlock_irqrestore(&tdc->lock, flags); >> dma_desc->txd.flags = 0; >> > > I think we should mark this for stable as well. I would make this the > 2nd patch in the series as it is related to #1. Okay!