From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hugh Dickins <hugh@veritas.com>
Subject: Re: [PATCH 2/2] check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/
Date: Fri, 24 Apr 2009 05:29:51 +0100 (BST)
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Joe Malicki <jmalicki@metacarta.com>,
	Michael Itz <mitz@metacarta.com>,
	Kenneth Baker <bakerk@metacarta.com>,
	Chris Wright <chrisw@sous-sol.org>,
	David Howells <dhowells@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
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On Fri, 23 Apr 2009, Oleg Nesterov wrote:
>  	write_lock(&p->fs->lock);
> -	lock_task_sighand(p, &flags);
> +	rcu_read_lock();
>  	for (t = next_thread(p); t != p; t = next_thread(t)) {
>  		if (t->fs == p->fs)
>  			n_fs++;
>  	}
> +	rcu_read_lock();

Not quite! if second rcu_read_lock() changed to rcu_read_unlock(), then
Acked-by: Hugh Dickins <hugh@veritas.com>