On Thu, 1 Apr 2010, Oleg Nesterov wrote:

quoted text
> proc_oom_score(task) have a reference to task_struct, but that is all.
> If this task was already released before we take tasklist_lock
> 
> 	- we can't use task->group_leader, it points to nowhere
> 
> 	- it is not safe to call badness() even if this task is
> 	  ->group_leader, has_intersects_mems_allowed() assumes
> 	  it is safe to iterate over ->thread_group list.
> 
> 	- even worse, badness() can hit ->signal == NULL
> 
> Add the pid_alive() check to ensure __unhash_process() was not called.
> 
> Also, use "task" instead of task->group_leader. badness() should return
> the same result for any sub-thread. Currently this is not true, but
> this should be changed anyway.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: David Rientjes <rientjes@google.com>

Andrew, this is 2.6.34 material and should be backported to stable.  It's 
not introduced by the recent oom killer rewrite pending in -mm, but it 
will require a trivial merge resolution on that work.
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