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Date:   Sat, 20 Jan 2018 18:48:52 +0000
From:   Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To:     Gaurav Kohli <gkohli@codeaurora.org>
Cc:     jslaby@suse.com, gregkh@linuxfoundation.org, mikey@neuling.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        stable@kernel.org
Subject: Re: [PATCH V1] tty: fix data race between tty_init_dev and flush of
 buf
Message-ID: <20180120184852.456d92ad@alans-desktop>
In-Reply-To: <1516195459-1080-1-git-send-email-gkohli@codeaurora.org>
References: <1516195459-1080-1-git-send-email-gkohli@codeaurora.org>
Organization: Intel Corporation
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On Wed, 17 Jan 2018 18:54:19 +0530
Gaurav Kohli <gkohli@codeaurora.org> wrote:

> There can be a race, if receive_buf call comes before
> tty initialization completes in n_tty_open and tty->disc_data
> may be NULL.
> 
> CPU0					CPU1
> ----					----
>  000|n_tty_receive_buf_common()   	n_tty_open()
> -001|n_tty_receive_buf2()		tty_ldisc_open.isra.3()
> -002|tty_ldisc_receive_buf(inline)	tty_ldisc_setup()
> 
> Using ldisc semaphore lock in tty_init_dev till disc_data
> initializes completely.
> 
> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>

Reviewed-by: Alan Cox <alan@linux.intel.com>

Alan