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Wed, 23 Sep 2026 15:23:42 +0000 Date: Wed, 23 Sep 2026 10:23:33 -0500 From: Frank Li To: Ginger Li Cc: sean.wang@mediatek.com, vkoul@kernel.org, Frank.Li@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dmaengine: milbeaut-hdmac: Fix deadlock with the channel IRQ handler Message-ID: References: <20260923094426.67872-1-ginger.jzllee@gmail.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260923094426.67872-1-ginger.jzllee@gmail.com> X-ClientProxiedBy: PH7P220CA0179.NAMP220.PROD.OUTLOOK.COM (2603:10b6:510:33b::27) To GV2PR04MB11799.eurprd04.prod.outlook.com (2603:10a6:150:2cf::9) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: GV2PR04MB11799:EE_|VI0PR04MB10928:EE_ X-MS-Office365-Filtering-Correlation-Id: 6cd48f3f-a39b-4890-624c-08df1986a666 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|7416014|376014|19092799006|1800799024|6133799003|11063799006|10067099003|56012099006|18002099003|22082099003; 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Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] > > milbeaut_hdmac_interrupt() is a hardirq handler and takes mc->vc.lock with a > plain spin_lock() for the whole time it runs. interrupts are disabled locally > in that context, so the handler itself is fine. > > milbeaut_hdmac_chan_config(), milbeaut_hdmac_chan_pause() and > milbeaut_hdmac_chan_resume() are called from process context and take the same > lock with a plain spin_lock() as well, so interrupts stay enabled while the > lock is held. > > If a channel interrupt is delivered on the CPU that is inside one of those > critical sections, milbeaut_hdmac_interrupt() spins on a lock that the > interrupted code is holding and can never release, and the CPU hangs. > > Take mc->vc.lock with spin_lock_irqsave() in those three functions, as > milbeaut_hdmac_issue_pending() and the other process context users of this > lock already do. > > Fixes: 6c3214e698e4 ("dmaengine: milbeaut-hdmac: Add HDMAC driver for Milbeaut platforms") > Signed-off-by: Ginger Li > --- Reviewed-by: Frank Li > drivers/dma/milbeaut-hdmac.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/drivers/dma/milbeaut-hdmac.c b/drivers/dma/milbeaut-hdmac.c > --- a/drivers/dma/milbeaut-hdmac.c > +++ b/drivers/dma/milbeaut-hdmac.c > @@ -214,10 +214,11 @@ milbeaut_hdmac_chan_config(struct dma_chan *chan, stru > { > struct virt_dma_chan *vc = to_virt_chan(chan); > struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc); > + unsigned long flags; > > - spin_lock(&mc->vc.lock); > + spin_lock_irqsave(&mc->vc.lock, flags); > mc->cfg = *cfg; > - spin_unlock(&mc->vc.lock); > + spin_unlock_irqrestore(&mc->vc.lock, flags); > > return 0; > } > @@ -226,13 +227,14 @@ static int milbeaut_hdmac_chan_pause(struct dma_chan * > { > struct virt_dma_chan *vc = to_virt_chan(chan); > struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc); > + unsigned long flags; > u32 val; > > - spin_lock(&mc->vc.lock); > + spin_lock_irqsave(&mc->vc.lock, flags); > val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACA); > val |= MLB_HDMAC_PB; > writel_relaxed(val, mc->reg_ch_base + MLB_HDMAC_DMACA); > - spin_unlock(&mc->vc.lock); > + spin_unlock_irqrestore(&mc->vc.lock, flags); > > return 0; > } > @@ -241,13 +243,14 @@ static int milbeaut_hdmac_chan_resume(struct dma_chan > { > struct virt_dma_chan *vc = to_virt_chan(chan); > struct milbeaut_hdmac_chan *mc = to_milbeaut_hdmac_chan(vc); > + unsigned long flags; > u32 val; > > - spin_lock(&mc->vc.lock); > + spin_lock_irqsave(&mc->vc.lock, flags); > val = readl_relaxed(mc->reg_ch_base + MLB_HDMAC_DMACA); > val &= ~MLB_HDMAC_PB; > writel_relaxed(val, mc->reg_ch_base + MLB_HDMAC_DMACA); > - spin_unlock(&mc->vc.lock); > + spin_unlock_irqrestore(&mc->vc.lock, flags); > > return 0; > } > -- > 2.43.0 >