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Wed, 1 Jul 2020 06:43:28 +0000 Subject: Re: UART/TTY console deadlock To: Tony Lindgren , Sergey Senozhatsky Cc: Petr Mladek , Andy Shevchenko , Raul Rangel , Sergey Senozhatsky , linux-kernel , Greg Kroah-Hartman , Andy Shevchenko , kurt@linutronix.de, "S, Shirish" , Peter Zijlstra , John Ogness , Steven Rostedt References: <20200630035816.GA21591@jagdpanzerIV.localdomain> <20200630102141.GA11587@alley> <20200630105512.GA530@jagdpanzerIV.localdomain> <20200630122239.GD6173@alley> <20200630130534.GB145027@jagdpanzerIV.localdomain> <20200630180255.GD37466@atomide.com> From: "S, Shirish" Message-ID: <3b665cbd-7afb-b72d-22c0-7dc1543ac42e@amd.com> Date: Wed, 1 Jul 2020 12:14:35 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 In-Reply-To: <20200630180255.GD37466@atomide.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-ClientProxiedBy: BM1PR01CA0124.INDPRD01.PROD.OUTLOOK.COM (2603:1096:b00:40::18) To CH2PR12MB3784.namprd12.prod.outlook.com (2603:10b6:610:21::28) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.252.85.182] (165.204.159.242) by BM1PR01CA0124.INDPRD01.PROD.OUTLOOK.COM (2603:1096:b00:40::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3153.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 34440ad8-f26b-42b5-d426-08d81d8a0fe3 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Jul 2020 06:43:28.6744 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 3Pbpj0CWNap+CNhvd0alFcRB/uJhCiWV9OjPiR//OYm7qZAkNNu3Koo7AnQYEYMZ/RVtr31p7o8Xf7liU4fXtQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4183 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/30/2020 11:32 PM, Tony Lindgren wrote: > * Sergey Senozhatsky [200630 13:06]: >> On (20/06/30 14:22), Petr Mladek wrote: > ... > >>>>>> @@ -2284,8 +2289,6 @@ int serial8250_do_startup(struct uart_port *port) >>>>>> * allow register changes to become visible. >>>>>> */ >>>>>> spin_lock_irqsave(&port->lock, flags); >>>>>> - if (up->port.irqflags & IRQF_SHARED) >>>>>> - disable_irq_nosync(port->irq); >>>>>> >>>>>> wait_for_xmitr(up, UART_LSR_THRE); >>>>>> serial_port_out_sync(port, UART_IER, UART_IER_THRI); >>>>>> @@ -2297,9 +2300,9 @@ int serial8250_do_startup(struct uart_port *port) >>>>>> iir = serial_port_in(port, UART_IIR); >>>>>> serial_port_out(port, UART_IER, 0); >>>>>> >>>>>> - if (port->irqflags & IRQF_SHARED) >>>>>> - enable_irq(port->irq); >>>>>> spin_unlock_irqrestore(&port->lock, flags); >>>>>> + if (irq_shared) >>>>>> + enable_irq(port->irq); >>>>>> >>>>>> /* >>>>>> * If the interrupt is not reasserted, or we otherwise >>>>> I think that it might be safe but I am not 100% sure, sigh. >>>> Yeah, I'm not 100%, but I'd give it a try. >>> I do not feel brave enough to ack it today. But I am all for trying it >>> if anyone more familiar with the code is fine with it. >> I see. Well, I suppose we need Ack-s from tty/serial/8250 maintainers. >> I would not be very happy if _only_ printk people Ack the patch. FWIW, the lockdep trace is not seen anymore with the patch applied. Regards, Shirish S > This conditional disable for irq_shared does not look nice to me > from the other device point of view :) > > Would it be possible to just set up te dummy interrupt handler > for the startup, then change it back afterwards? See for example > omap8250_no_handle_irq(). > > The other device for irq_shared should be capable of dealing > with spurious interrupts if it's shared. > > Regards, > > Tony -- Regards, Shirish S