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Date: Thu, 5 Dec 2013 15:23:55 -0800 (PST)
From: David Rientjes <rientjes@google.com>
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To: Oleg Nesterov <oleg@redhat.com>
cc: Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
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        Sameer Nanda <snanda@chromium.org>, Sergey Dyasly <dserrg@gmail.com>,
        "Tu, Xiaobing" <xiaobing.tu@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/4] introduce for_each_thread() to replace the buggy
 while_each_thread()
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On Thu, 5 Dec 2013, Oleg Nesterov wrote:

> > Minor: should the definitions of thread_{head,node} be annotated with
> > __rcu for users of CONFIG_SPARSE_RCU_POINTER?
> 
> Perhaps. And perhaps task_struct->tasks. And perhaps we should add
> rcu_read_lock_held() || lockdep_is_held(tasklist) || lockdep_is_held(siglock)
> into for_each_process/thead.
> 
> But lets do this later. At least we should avoid the false positives.
> 

Ok, thanks.  I think anything we can do to catch these cases of 
unprotected usage even with some debugging options like 
CONFIG_SPARSE_RCU_POINTER and CONFIG_LOCKDEP will help given the number of 
places you found that were doing it incorrectly already.