From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsOWBI4Y73aP/QJC6YjjafNRaZzZiqG72hj+5wrjbVaC5d7fcz3+794WJRrD704ii79yALw ARC-Seal: i=1; a=rsa-sha256; t=1521214859; cv=none; d=google.com; s=arc-20160816; b=UqhfD8lYuW3d5AV9GqBy38LI/T32RRvTErQF5IefsYdsVTSl38ZTG8QkpxqI+qiKO7 9OD3XkX+17gKhrId7PxnkVKfrWMGb99wHjWI/Sr7vvetATMC3vqw1yWkBRp6ViTcAdlH GqSidMH23YI5v/D6rdf9ZFl1bwIwhsOhnQu3aqoQ8ZiHSCyIsSUZczf0SizKJRXeTj4e 1XuBaNp7lqE5AQuPwGZ2iw0xO+lgxawEiokRyFt4GfK1fVXZYp1e2GocZNWpQMq/Iybd 2SBDEVznztgr7WVWKDJCEx5Xv8NHJHfWMlkOakXCVKIWihz3j+RRAYs5GGHK2+hzpAll ehuQ== 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=Yr7k/eOEJOv0/8NwK2sHLymB27YcjSlIXekZvtEumnM=; b=egiDr9dB+wVgLZAF59SmNY2LYE8wNJyciCXKyFvj1UR+BWeG+vjjKqYurE+IULXjPB ib9mXtt5wxwOxMnW5cFoOvV+72Jnu04fAPsfkT+cjqmuqq+1MYYeBexz/CFn8FAuVqqs /oQUaCjPi0vEFgmU6eefmjpWRLn+BLWUyo0f88YqNK94LV1gMsNhNxNg1yFR0NW3ON5Z bLHrwXe22tEJSYD9Iv8LnnHsZPQta5YK3DRzuig+L/G8v0nlqZZkMn5P4bLKphMj3wK/ LyO9uno8GLdbFMa5YtzPiWQNayg8lqjTpihN+BZbeos6r7Q6h3oyQFqrzAghCcTr7CyJ itCA== 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 4.15 009/128] serial: sh-sci: prevent lockup on full TTY buffers Date: Fri, 16 Mar 2018 16:22:30 +0100 Message-Id: <20180316152336.670371434@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180316152336.199007505@linuxfoundation.org> References: <20180316152336.199007505@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?1595109392350436061?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-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 @@ -885,6 +885,8 @@ 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)); }