linux-kernel - Re: [PATCH 1/1] Char: vt, make sysfs operations atomic

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Message-ID: <20080527194357.GA12185@cathedrallabs.org>
Date:	Tue, 27 May 2008 15:43:57 -0400
From:	Aristeu Rozanski <aris@...vo.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 1/1] Char: vt, make sysfs operations atomic

> Hold console sem while creating/destroying sysfs files. Serialisation is
> so far done by BKL held in tty release_dev and chrdev_open, but no other
> locks are held in open path.
> 
>  				tty->termios->c_iflag |= IUTF8;
>  			else
>  				tty->termios->c_iflag &= ~IUTF8;
> -			release_console_sem();
>  			vcs_make_sysfs(tty);
> +			release_console_sem();
>  			return ret;
>  		}
>  	}
> @@ -2772,8 +2772,8 @@ static void con_close(struct tty_struct *tty, struct file *filp)
>  		if (vc)
>  			vc->vc_tty = NULL;
>  		tty->driver_data = NULL;
> -		release_console_sem();
>  		vcs_remove_sysfs(tty);
> +		release_console_sem();
>  		mutex_unlock(&tty_mutex);
>  		/*
>  		 * tty_mutex is released, but we still hold BKL, so there is
the reason for the code be the way it is is because vcs_{add,remove}_sysfs()
may sleep

-- 
Aristeu

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