From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 30C2522D7A6; Mon, 10 Mar 2025 17:59:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741629551; cv=none; b=WyTJIa4BF6Xl7ipyFtIG0TUfOYaJsZU7vi8rju25ylpns22wdPPJUgdxYlNZC11pXHVSmoULwapwN6GglfES/0ftG0LF9TYcxyrbj+Vffdl3Y8fBiR5PhVKWIw/a3znZULwfHbK12C6Y+pRS4tExq+iG8EJO7tzZ6QEfc97c0O0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741629551; c=relaxed/simple; bh=JsyC1fXxLqPqqbLZMoa0jYuJ9CzX1D7PWlPmb65TCcs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HhBAxXUpc5GnaHj7jx3fgG/p9VVUlYAqj5ivA2YPzEvBjEeMv0hwOn2CzlnUtG+Z3957RCLq2IgP3RLvODLLrmzwAjbEYD78pVeXpziT0UCzNsGctuz/hkZG3z/bYi5P73zUk025P3UzdtRvcdbr00iPKNi/GBnpNNtaYvxq1Xk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PYn0X0Mt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="PYn0X0Mt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 529A4C4CEE5; Mon, 10 Mar 2025 17:59:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741629550; bh=JsyC1fXxLqPqqbLZMoa0jYuJ9CzX1D7PWlPmb65TCcs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PYn0X0Mtzt8ohiMuWraFf0ppLRUs6RMF4BDkHfPy0cfC1gBwWRmZkXI54drfaeR1W bCR6wxlTfKnCcncG/eIfiYWddSwyI5hF75JIS3Jrmkeco7iy6G6ng/Fxutw6wHsex1 mAmHCmSpVf8ykf3qVNIldsZcUOyWdHA0o9CCPNrI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sean Anderson , John Ogness Subject: [PATCH 5.15 334/620] tty: xilinx_uartps: split sysrq handling Date: Mon, 10 Mar 2025 18:03:00 +0100 Message-ID: <20250310170558.795457624@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250310170545.553361750@linuxfoundation.org> References: <20250310170545.553361750@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Anderson commit b06f388994500297bb91be60ffaf6825ecfd2afe upstream. lockdep detects the following circular locking dependency: CPU 0 CPU 1 ========================== ============================ cdns_uart_isr() printk() uart_port_lock(port) console_lock() cdns_uart_console_write() if (!port->sysrq) uart_port_lock(port) uart_handle_break() port->sysrq = ... uart_handle_sysrq_char() printk() console_lock() The fixed commit attempts to avoid this situation by only taking the port lock in cdns_uart_console_write if port->sysrq unset. However, if (as shown above) cdns_uart_console_write runs before port->sysrq is set, then it will try to take the port lock anyway. This may result in a deadlock. Fix this by splitting sysrq handling into two parts. We use the prepare helper under the port lock and defer handling until we release the lock. Fixes: 74ea66d4ca06 ("tty: xuartps: Improve sysrq handling") Signed-off-by: Sean Anderson Cc: stable@vger.kernel.org # c980248179d: serial: xilinx_uartps: Use port lock wrappers Acked-by: John Ogness Link: https://lore.kernel.org/r/20250110213822.2107462-1-sean.anderson@linux.dev Signed-off-by: Sean Anderson Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/xilinx_uartps.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -268,7 +268,7 @@ static void cdns_uart_handle_rx(void *de continue; } - if (uart_handle_sysrq_char(port, data)) + if (uart_prepare_sysrq_char(port, data)) continue; if (is_rxbs_support) { @@ -385,7 +385,7 @@ static irqreturn_t cdns_uart_isr(int irq !(readl(port->membase + CDNS_UART_CR) & CDNS_UART_CR_RX_DIS)) cdns_uart_handle_rx(dev_id, isrstatus); - spin_unlock(&port->lock); + uart_unlock_and_check_sysrq(port); return IRQ_HANDLED; } @@ -1217,10 +1217,8 @@ static void cdns_uart_console_write(stru unsigned int imr, ctrl; int locked = 1; - if (port->sysrq) - locked = 0; - else if (oops_in_progress) - locked = spin_trylock_irqsave(&port->lock, flags); + if (oops_in_progress) + locked = uart_port_trylock_irqsave(port, &flags); else spin_lock_irqsave(&port->lock, flags);