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

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Date:	Tue, 27 May 2008 22:27:26 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Aristeu Rozanski <aris@...vo.org>
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

On 05/27/2008 09:43 PM, Aristeu Rozanski wrote:
>> 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

What's the point? To have races in the code but not sleep inside the semaphore?
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