From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 0FB3F38F92A for ; Thu, 16 Apr 2026 09:29:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776331797; cv=none; b=KUwX9pQluOW6MftfMMUPGpfhV4nx2d8YOi/MFTbs2qtexKNjpelD6JpluobKbs78/biHx/b/pemrnPBGmZiPYEUujKUfrKAu6QIoAMZMPBXIVg8Qu8EYRFXAlsFqvbp/B7nbofzuvptLiVbuamMy5eRnvv0PawkxOZXel9P5cd8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776331797; c=relaxed/simple; bh=IN1c6EBVtDwVZ/i+Hsq84OXuF2BWcajy1Gk01ydTT3g=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=naSH4U0dNZW9anfCskUjxP4xJrg6tD/mu1vE6ZW3kaHtIUHPTQxF+gGr8Mvnl7xxt3EfVd6eHy1RTuqvlMUVleCzyyd+gqQspcCWDnqdQzIgACq8ijIErn0lPBvTdIaW4gp/AhIXK04GbADMGs8zr5RlxUeaG6FweyKc8OxupRk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=gxBZboNk; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="gxBZboNk" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776331783; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=LvbGqp3piMlc8p/ePjRSqAyHONR2DqDhp9yAF1uUqrI=; b=gxBZboNkzdT8myaVFQi2LRtp58HEnJHb/uMLyRlU2UHeOVeZ7RySGIkZUZXKk1vOFcWKAI 1mYzMjWHiNvI+hDZ57fXLxaO3aqVe8UzHRlPm/E3WgkcrzlTN9WKemkxfzQLxOH7/ppagI hbcYOgbj8PuWCKpPVY82dyQvcMynvTs= From: Fushuai Wang To: gregkh@linuxfoundation.org, jirislaby@kernel.org, ilpo.jarvinen@linux.intel.com, osama.abdelkader@gmail.com, andy.shevchenko@gmail.com, kees@kernel.org Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, wangfushuai@baidu.com Subject: [PATCH] serial: 8250: Clear CON_PRINTBUFFER on port re-registration Date: Thu, 16 Apr 2026 17:29:17 +0800 Message-Id: <20260416092917.27301-1-fushuai.wang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Fushuai Wang When two PnP devices map to the same physical port, the serial8250 driver removes and re-registers the console structure for the same port. During re-registration, the console structure still has CON_PRINTBUFFER set from the initial registration, which causes console_init_seq() to set console->seq to syslog_seq. This results in re-printing the entire system log buffer, which may lead to RCU stall on slow serial consoles. Clear CON_PRINTBUFFER when re-registering a port to prevent duplicate log printing. Signed-off-by: Fushuai Wang --- drivers/tty/serial/8250/8250_core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index d2e2c5dfef99..3465a4d93b50 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -694,6 +694,7 @@ int serial8250_register_8250_port(const struct uart_8250_port *up) { struct uart_8250_port *uart; int ret; + bool was_removed = false; if (up->port.uartclk == 0) return -EINVAL; @@ -716,8 +717,10 @@ int serial8250_register_8250_port(const struct uart_8250_port *up) if (uart->port.type == PORT_8250_CIR) return -ENODEV; - if (uart->port.dev) + if (uart->port.dev) { uart_remove_one_port(&serial8250_reg, &uart->port); + was_removed = true; + } uart->port.ctrl_id = up->port.ctrl_id; uart->port.port_id = up->port.port_id; @@ -819,6 +822,10 @@ int serial8250_register_8250_port(const struct uart_8250_port *up) &uart->capabilities); serial8250_apply_quirks(uart); + + if (was_removed && uart_console(&uart->port)) + uart->port.cons->flags &= ~CON_PRINTBUFFER; + ret = uart_add_one_port(&serial8250_reg, &uart->port); if (ret) -- 2.36.1