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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0CFBFCD5BAB for ; Sun, 24 May 2026 19:42:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5Qbk2Js+U5TVltxF7DmfkdpZCQrfZY8VcWdcdlf8tJQ=; b=1oDOZs3s4lY9Wa9TJvHo4XwDM9 4peX8g500woD29NYfP+2fDp37Qo4Mvfs0+BooBiVR3CucW6/HfkOc1y5GqMT9yrPrgySevbmFIYZY 1FJdcDrgC2icYpN8EsvCF7LceVb/d1QEXJyx594Rrej9xYheYiXlRNWqweK0O62JzazNF2NJM5zfA rok8ElnX34qjVAXelITGShLcQ2gajnI2ip8Nf0vUQmJlVGdv/5hVc1eDUVClvts4eQDAM7ye9N6Kl DhLxu1df2BKacSIh8leBIk201WRodsn85YsoynUjlj7U5E7qS4HaUttZUKagvrp+EYRXwpgSvr20X IU5QRORA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wREiG-0000000FWLU-0Xx9; Sun, 24 May 2026 19:42:16 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wREiF-0000000FWLE-17A6 for linux-arm-kernel@lists.infradead.org; Sun, 24 May 2026 19:42:15 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id CAAC8601F4; Sun, 24 May 2026 19:42:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32B3E1F000E9; Sun, 24 May 2026 19:42:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779651733; bh=5Qbk2Js+U5TVltxF7DmfkdpZCQrfZY8VcWdcdlf8tJQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iZb2Qfmltboafv45n9a51F+qDWhaK733kQGT2ABAw9GJv0WPs4sYPWJMkYBrMpW76 84bfCmBxjpODVz4HcUDEpWrhSkXvW/D1by+hOZyX1DJaOqHhCLJxyhaYy3ZS30sDZR doJES/dfPScYEE85hYtIjEOpT6tG5WvwgwKORpvTKKPeSA6jvxFO8TlPj4qyic62Ea bzD/f5f6tcd4OnajOVxK95QqB2DR+mg2ebPTSeCXtVUUuLmDMax85rzaK+hTzG/B8E ifhiwn6cOs7ODHGxJk9ltYtrAK0KsRojltv92B7OydVVEY191AcRu0/5BmLSuDGsh3 9VbImlmVHvx5w== Message-ID: Date: Sun, 24 May 2026 21:42:08 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tty: serial: samsung: Remove redundant port lock acquisition in rx helpers To: Tudor Ambarus , Alim Akhtar , Greg Kroah-Hartman , Jiri Slaby , Ben Dooks Cc: linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, john.ogness@linutronix.d, peter.griffin@linaro.org, andre.draszik@linaro.org, jyescas@google.com, kernel-team@android.com, stable@vger.kernel.org, John Ogness References: <20260515-samsung-tty-flow-control-deadlock-v1-1-93255edbc9bc@linaro.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 15/05/2026 14:41, Tudor Ambarus wrote: > Sashiko identified a deadlock when the console flow is engaged [1]. > > When console flow control is enabled (UPF_CONS_FLOW), > s3c24xx_serial_stop_tx() calls s3c24xx_serial_rx_enable() and > s3c24xx_serial_start_tx() calls s3c24xx_serial_rx_disable(). > > The serial core framework invokes the .stop_tx() and .start_tx() > callbacks with the port->lock spinlock already held. Furthermore, all > internal driver paths that invoke stop_tx (such as the DMA TX > completion handler s3c24xx_serial_tx_dma_complete() or the PIO TX IRQ > handler s3c24xx_serial_tx_irq()) also acquire port->lock prior to > calling it. (Note that s3c24xx_serial_start_tx() is only invoked by the > serial core). > > However, s3c24xx_serial_rx_enable() and s3c24xx_serial_rx_disable() > unconditionally attempt to acquire port->lock again using > uart_port_lock_irqsave(). Since spinlocks are not recursive, this > causes a deadlock on the same CPU when console flow control is engaged. > > Remove the redundant lock acquisition from both rx helper functions. > Acked-by: Krzysztof Kozlowski Best regards, Krzysztof