From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C33651F4180; Sun, 24 May 2026 19:42:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779651734; cv=none; b=V2rash17izNGsmMu5LUz2Zl6oB9p0S3cvRjmU6DWik55ip+Kak0/gRLdGxKcJBfPQR8JKHvn3VaieJxUTTQdbMEKhAqzyCiLYoF2sUwBicDIkyPAQS6LA96julaz7ximkQBxKrRfGhmZyyZiECbvN+PcqACPIjuxq0XlUvXaLPw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779651734; c=relaxed/simple; bh=lthXzUytBGGEZEbaMRp/d7G3sIqZTOorIRP0QYBN0Cw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hqfzkX46mm/Lg0y2miXinJImLgz0/CgE807EYJ/shy9vnobwZJqYyFooYEqJ6fJmDE0r9hvS6ZgGa4ajsE4iIw+k22Z1etFdMK+2ScQKy4H6DVJeSCMUr1WqGb0tKmEhtbruIe3X07DN8HScgOx1LL6N2hqzWbyIzktTnIhk3MA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iZb2Qfml; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iZb2Qfml" 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 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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