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 4544F3242DF; Sun, 7 Jun 2026 10:56:51 +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=1780829812; cv=none; b=dn+afx16w+INpNsbi4N6AqhqZ/ZQKGn+cjEEwe3SsMjAr7ogPxAcUqjqOBwn/kdsLPpZxUkwZWH2XrlqiUQesporMBpWcFFxx06wgKBaxOWCZ4UDwrlN/eoH3F5LQ1qnsif4f2B5AECXEPV7lj7Kzt3NkN6Z1j1qmytUNXV/wzA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780829812; c=relaxed/simple; bh=6qqY0AewLkFknwKTjbUbCJKsTjtY8EZwfYWVG7RDip8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=YAUPAtQpAVST1iOvaCeY5jOOVlJCNNEWUtPw/lf1lD0/nZaVvB8EgG48DLvln6AghNzROktFE4xrWO2Reo1JpNLskfVhrXSXY8FnQMNXxDKP09INCxf2MMXLN8jlFOwnpaURfULtQQt1I5/OueVYcXfvmVlneRJVTpPGCTi3KIo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vqlaoI2j; 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="vqlaoI2j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 871AB1F00893; Sun, 7 Jun 2026 10:56:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780829811; bh=NDyN2wbk6WsCkjycMhg3/fCgUrXEVC4kMj5l4ary3pk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vqlaoI2j/qIUOfK0cXzP9HwaS+xwKciIdfaWdyUr0yITuSK9eSwR54bFvTucgKlm9 cXgiiBBeCRT6KliTiQ+Xc4oqGheTHBz6S1TZMqitMAIHUuNIovTcPKL2OR1rq5Z3HW RH6qAB8q76pZbxYokAvlJ6s+DAocYgkq5TsGQa3o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Jacques Nilo Subject: [PATCH 6.18 280/315] serial: 8250: dispatch SysRq character in serial8250_handle_irq() Date: Sun, 7 Jun 2026 12:01:07 +0200 Message-ID: <20260607095737.873581177@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260607095727.528828913@linuxfoundation.org> References: <20260607095727.528828913@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jacques Nilo commit 71f42b2149a1307a97165b409493665579462ea0 upstream. serial8250_handle_irq() captures a SysRq character into port->sysrq_ch inside serial8250_handle_irq_locked() via uart_prepare_sysrq_char() (reached from serial8250_read_char()). Dispatch of that captured character to handle_sysrq() is expected to happen at port-unlock time, through uart_unlock_and_check_sysrq[_irqrestore](). After commit 8324a54f604d ("serial: 8250: Add serial8250_handle_irq_locked()") the function was reduced to a wrapper that takes the port lock via guard(uart_port_lock_irqsave) whose destructor is plain uart_port_unlock_irqrestore(). The sysrq-aware unlock helper is no longer called, so port->sysrq_ch is captured but never dispatched: BREAK + SysRq key is consumed silently. This was the very condition Johan Hovold's 853a9ae29e978 ("serial: 8250: fix handle_irq locking", 2021) introduced uart_unlock_and_check_sysrq_irqrestore() to address. Switch to the new guard(uart_port_lock_check_sysrq_irqsave), whose destructor is the sysrq-aware unlock helper, restoring the pre-split behaviour. Update the Context: comment on serial8250_handle_irq_locked() so future HW-specific 8250 wrappers know to use the same guard or the explicit sysrq-aware unlock. Verified on RTL8196E with CONFIG_MAGIC_SYSRQ_SERIAL=y: BREAK + 'h' on the console UART produces the SysRq help dump in dmesg and the brk counter in /proc/tty/driver/serial increments correctly. Fixes: 8324a54f604d ("serial: 8250: Add serial8250_handle_irq_locked()") Cc: stable@vger.kernel.org Reviewed-by: Ilpo Järvinen Signed-off-by: Jacques Nilo Link: https://patch.msgid.link/52692ae6c3501f7940347cef364ad7fcacaab7e5.1778675349.git.jnilo@free.fr Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index af78cc02f38e..c66ba714caa5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1784,7 +1784,10 @@ static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir) } /* - * Context: port's lock must be held by the caller. + * Context: port's lock must be held by the caller. The caller must + * release it via guard(uart_port_lock_check_sysrq_irqsave) or + * uart_unlock_and_check_sysrq_irqrestore(), which captures SysRq + * character on unlock. */ void serial8250_handle_irq_locked(struct uart_port *port, unsigned int iir) { @@ -1837,7 +1840,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) if (iir & UART_IIR_NO_INT) return 0; - guard(uart_port_lock_irqsave)(port); + guard(uart_port_lock_check_sysrq_irqsave)(port); serial8250_handle_irq_locked(port, iir); return 1; -- 2.54.0