From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELvc8c8gIOuoa4eyvgDaj1nbM3c1KE7PFIciJw55bgltglJWHEubHwcNj+TPtxUc2RuSTacg ARC-Seal: i=1; a=rsa-sha256; t=1521214383; cv=none; d=google.com; s=arc-20160816; b=T9v0RaJLRLsK1VY1SYxpXjTe6er/bOErWXCtpvokuFaOKlfYrIxnT6PM3t56J7YXdC ExNPmY9pZVBZgsSLZIeuX3oPX3iKSR5yxQtngMCyOpZue8vUFJBymYVhbr30Ezk1AOS1 UIYm0T/K22hayO6u4J9x0JYXHAYkhn0RL1MXrosLtjyf1vx5NL81SqBK9fx2v7gDeCdy KOXn8wBQTizBntdC3iGW1iWsdgOGVFD9icZP4bq7ZP9TwpoSmDXDofDFtGRJT4VXTDhP 2QAeL0VOXebNclCwpgAZCS9/uR+B+SwwjT4KnT022rSHIqyW/l7hETjDbGKQEB80Nl01 z7jA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=IdknCDyjaxyuI+3FILbqewgVq/Jfbh27rKj9ZEifkwA=; b=EU+YOnhaUVaGAWafVZEJQnuqSGtp0U9dFfP0rIDrfCil16tKnFht2i8wi+byLBeB8f TZAs4oX5G0aJmvAOuEzIGpwdZAffv/utstGYxomPhOPdEbl+miLNQ6nLKPyHSutQCSRB 0qsb2EFt6/fcRHtEIV/h+mfgCnyRB/Y/r4yImlfS6ZSzKG5NSvYIrE3h9ORibptjxsO2 DVrDZCRRdcWgsAyqrPuRSEUy2/0dgZEh2LBvV1eJt+pXrmEbBWOYCHa0yzKzPFh2cPg+ NXd65eYkZNt2/RPfUpbDLjxLucKS7vEG3Cl+a/3ffyLkYqblku7jITBsUYXBR4FuSVm8 yBwA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yoshihiro Shimoda , Ulrich Hecht , Geert Uytterhoeven , Nguyen Viet Dung Subject: [PATCH 4.9 73/86] serial: sh-sci: prevent lockup on full TTY buffers Date: Fri, 16 Mar 2018 16:23:36 +0100 Message-Id: <20180316152322.278253230@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180316152317.167709497@linuxfoundation.org> References: <20180316152317.167709497@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1595108493927910261?= X-GMAIL-MSGID: =?utf-8?q?1595108893258272321?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ulrich Hecht commit 7842055bfce4bf0170d0f61df8b2add8399697be upstream. When the TTY buffers fill up to the configured maximum, a system lockup occurs: [ 598.820128] INFO: rcu_preempt detected stalls on CPUs/tasks: [ 598.825796] 0-...!: (1 GPs behind) idle=5a6/2/0 softirq=1974/1974 fqs=1 [ 598.832577] (detected by 3, t=62517 jiffies, g=296, c=295, q=126) [ 598.838755] Task dump for CPU 0: [ 598.841977] swapper/0 R running task 0 0 0 0x00000022 [ 598.849023] Call trace: [ 598.851476] __switch_to+0x98/0xb0 [ 598.854870] (null) This can be prevented by doing a dummy read of the RX data register. This issue affects both HSCIF and SCIF ports. Reported for R-Car H3 ES2.0; reproduced and fixed on H3 ES1.1. Probably affects other R-Car platforms as well. Reported-by: Yoshihiro Shimoda Signed-off-by: Ulrich Hecht Reviewed-by: Geert Uytterhoeven Cc: stable Tested-by: Nguyen Viet Dung Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sh-sci.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -935,6 +935,8 @@ static void sci_receive_chars(struct uar /* Tell the rest of the system the news. New characters! */ tty_flip_buffer_push(tport); } else { + /* TTY buffers full; read from RX reg to prevent lockup */ + serial_port_in(port, SCxRDR); serial_port_in(port, SCxSR); /* dummy read */ sci_clear_SCxSR(port, SCxSR_RDxF_CLEAR(port)); }