Re: [patch] oom: avoid killing kthreads if they assume the oom killed thread's mm

[David Rientjes <rientjes@google.com>]

On Tue, 26 Jul 2011, Michal Hocko wrote:

> > After selecting a task to kill, the oom killer iterates all processes and
> > kills all other threads that share the same mm_struct in different thread
> > groups.  It would not otherwise be helpful to kill a thread if its memory
> > would not be subsequently freed.
> > 
> > A kernel thread, however, may assume a user thread's mm by using
> > use_mm().  This is only temporary and should not result in sending a
> > SIGKILL to that kthread.
> 
> Good catch. Have you ever seen this happening?
> 

No, this is just another patch to make the kernel more use_mm()-friendly.  
Before that capability was introduced, it was possible to assume that a 
kthread would always have a NULL mm pointer, so it wasn't previously 
required for this code.

> > This patch ensures that only user threads and not kthreads are sent a
> > SIGKILL if they share the same mm_struct as the oom killed task.
> > 
> > Signed-off-by: David Rientjes <rientjes@google.com>
> 
> Reviewed-by: Michal Hocko <mhocko@suse.cz>

Thanks!

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