linux-kernel - Re: [PATCH] tty: hold lock across tty buffer finding and buffer filling

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Message-ID: <4F63101D.70507@suse.cz>
Date:	Fri, 16 Mar 2012 11:04:13 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	"Du, Alek" <alek.du@...el.com>
CC:	"jiris >> Jiri Slaby" <jirislaby@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Tu, Xiaobing" <xiaobing.tu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"Zhang, Yanmin" <yanmin.zhang@...el.com>,
	"Zuo, Jiao" <jiao.zuo@...el.com>
Subject: Re: [PATCH] tty: hold lock across tty buffer finding and buffer filling

On 03/16/2012 11:01 AM, Du, Alek wrote:
> We prepared the buffer, and use it. And during this, we don't release the spinlock of buf.lock, how the flush could happen?
> 
>                A
> spin_lock
> prepare the buffer
> user the buffer
> spin unlock
> 
> 
>               B
> Spin_lock
> Flush
> Free the buffer
> Put buf.tail = NULL
> Spin unlock

Well, you do. Not all drivers use tty_insert_flip_string. Take a look at
tty_prepare_flip_string and its users.

thanks,
-- 
js
suse labs
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