From: Al Viro <viro@ftp.linux.org.uk>
To: Roland Dreier <rdreier@cisco.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: [RESEND] file operations: release can race with read/write?
Date: Wed, 17 Oct 2007 20:33:21 +0100 [thread overview]
Message-ID: <20071017193320.GK8181@ftp.linux.org.uk> (raw)
In-Reply-To: <adaodexh9uz.fsf@cisco.com>
On Wed, Oct 17, 2007 at 11:30:44AM -0700, Roland Dreier wrote:
> static unsigned long flag;
>
> static int cw_open(struct inode *inode, struct file *filp)
> {
> return 0;
> }
>
> static int cw_close(struct inode *inode, struct file *filp)
> {
> clear_bit(1, &flag);
>
> msleep(1);
>
> if (test_and_set_bit(1, &flag))
> printk(KERN_ERR "Write raced with close?\n");
Of _course_ you can trigger that - just open two files and have write
on one of them while another gets closed.
That is certainly possible, but it has nothing whatsoever with the
race you've described - you have two different objects and method
call on one of them might happen when destructor is called on another.
You have protection against ->release() for a struct file called
while you are in ->write() for _same_ struct file.
next prev parent reply other threads:[~2007-10-17 19:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-16 18:53 file operations: release can race with read/write? Roland Dreier
2007-10-17 18:30 ` [RESEND] " Roland Dreier
2007-10-17 19:16 ` Andrew Morton
2007-10-17 22:06 ` Roland Dreier
2007-10-17 19:27 ` Al Viro
2007-10-17 19:33 ` Al Viro [this message]
2007-10-17 22:10 ` Roland Dreier
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