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Message-ID: <20071017192737.GJ8181@ftp.linux.org.uk> Date: Wed, 17 Oct 2007 20:27:37 +0100 From: Al Viro <viro@....linux.org.uk> To: Roland Dreier <rdreier@...co.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org Subject: Re: [RESEND] file operations: release can race with read/write? On Wed, Oct 17, 2007 at 11:30:44AM -0700, Roland Dreier wrote: > [Resending, directly to a couple likely suspects this time, in the > hope of getting a reply... thanks] > > I have a question about the synchronization of file_operations: is it > intended that the .release method of a file can be called while a > .read or .write method is still running for that file? > I've written a quick test case that seems to show this happen in > practice, and reading the code in fs/open.c and fs/read_write.c I see > no reason why this race can't happen: sys_read() and sys_write() just > do fget_light(), which will not increment the file's reference count > on the fast path, so a racing sys_close() from another thread could do > the final fput() that ends up calling the file's .release method > before the read or write has finished. If you _have_ another thread to call close() from, you won't hit that fast path. Case closed. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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