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 579B44E36D5; Thu, 17 Sep 2026 16:51:37 +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=1789663899; cv=none; b=Od0xzNGs0c9AzTT4HaRCFDMYFr8Th6E7Llv2KCKWs50KyP6acR8GN8Jbe0c7E6i9oJW/KKJNXUIMji3z+ZjtISDEB5g/rbkffMW3a8q+rdiDpKe5uSQQA5LHe+LdEAtOhsvkvH4S6HICktzYYO+HZnc+rxxeRTEHmdYRznOLAoA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789663899; c=relaxed/simple; bh=EN5jxOOWeTI89gdAUbP1rLXFJ8b8rwCwJy+RyznnLMg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KfXojvdfSqpMPCjIEKFwcUVf+uHRBTpjIPSROK3Euej1K0zIrzLrtxidn82dToDzY5pNxAcRrWKC9+nLnXN8MwQLNSGaMHIMh8iT5AwcSXqptgM+DT3FqCaDSRDdm2xzbnk0EIETJk1fLzD8wo4tUs1cjm2lnRyp7EdgvMVeXI8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FxKWwluQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FxKWwluQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E3D11F000FF; Thu, 17 Sep 2026 16:51:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789663897; bh=ZnUVxT0qADu2KwQNsG4aze+S1bLmdbHl9kr3c3wWN34=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FxKWwluQf/OfHLsOcloPdTnXSJy+XNkmYb36kQuYcvbhTEV7oy70GG4x7fQzD3WRf HdpuWRs/pep09lVjdaRwyQq8E+1JjAoiLSodTxlVTCWzI7kc76WrhbiILTllSAl070 63RWIpdwcxvyXeocL68TmHEs2P/+FBMqwgbgsOLM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Marco Felsch , Sasha Levin Subject: [PATCH 6.18 0191/1250] serial: 8250: fix possible ISR soft lockup Date: Thu, 17 Sep 2026 15:59:46 +0100 Message-ID: <20260917151557.291268582@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151551.901433442@linuxfoundation.org> References: <20260917151551.901433442@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marco Felsch [ Upstream commit 0c6bf45e5a345cc3b9ffbeaf9083ecac3c2293eb ] There are rare cases in which the host gets stuck in the ISR because it is flooded with messages during the startup phase. The reason for the soft lockup in the ISR is the missing FIFO error IRQ (FIFOE) handling. Not handling it and reporting IRQ_HANDLED triggers the IRQ immediately again. Fix this by adding a check for the FIFOE status and clearing the FIFO if no data is ready (DR). This behavior was observed on an AM62L device which uses the OMAP 8250 driver. Fix it for all 8250 drivers, since the OMAP driver's special IRQ setup handling may trigger this behavior more frequently, but it is not ensured that other 8250 drivers aren't affected. Signed-off-by: Marco Felsch Link: https://patch.msgid.link/20260519-v7-1-topic-serial-8250-v1-1-56b04293a246@pengutronix.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_port.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 9564a5d9b4d02..455d55827ada1 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1802,6 +1802,13 @@ void serial8250_handle_irq_locked(struct uart_port *port, unsigned int iir) status = serial_lsr_in(up); + /* + * Recover from no-data-ready and FIFO error condition to avoid getting + * stuck in the ISR. + */ + if (!(status & UART_LSR_DR) && (status & UART_LSR_FIFOE)) + serial8250_clear_and_reinit_fifos(up); + /* * If port is stopped and there are no error conditions in the * FIFO, then don't drain the FIFO, as this may lead to TTY buffer -- 2.53.0