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Date: Fri, 5 Dec 2014 20:16:47 +0000 (UTC)
From: Denis Du <dudenis2000@yahoo.ca>
Reply-To: Denis Du <dudenis2000@yahoo.ca>
To: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "jslaby@suse.cz" <jslaby@suse.cz>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Message-ID: <345838865.5722597.1417810607255.JavaMail.yahoo@jws10603.mail.bf1.yahoo.com>
In-Reply-To: <950568161.5257116.1417730252670.JavaMail.yahoo@jws10613.mail.bf1.yahoo.com>
References: <950568161.5257116.1417730252670.JavaMail.yahoo@jws10613.mail.bf1.yahoo.com>
Subject: TTY layer need a lock to copy data to user space
MIME-Version: 1.0
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	boundary="----=_Part_5722596_1074393473.1417810607254"
Sender: linux-kernel-owner@vger.kernel.org

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Hi, Guys:
It was found that the 3.12 kernel tty layer will lose or corrupt data when =
have a full-duplex communication, especcially in high baudrate, for example=
 230k for my OMAP5 uart. Eventually I found there is lock missing between c=
opy data to ldisc layer buffer and copy data from the same buffer to user=
=20
space. I believe this issue existed since 3.8 kernel(since this kernel , it=
 start to remove most of the spin-locks) and I didn't find any fix even thr=
ough 3.17 kernel. This patch was tested to be works great with no any data =
loss again.


I did try to use the existed lock atomic_read_lock, but it doesn=E2=80=99t =
work.=20


Denis Du
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