Re: [PATCH] oom: consider multi-threaded tasks in task_will_free_mem

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Michal Hocko wrote:
> > The whole thread group is going down does not mean we make sure that
> > we will send SIGKILL to other thread groups sharing the same memory which
> > is possibly holding mmap_sem for write, does it?
> 
> And the patch description doesn't say anything about processes sharing
> mm. This is supposed to be a minor fix of an obviously suboptimal
> behavior of task_will_free_mem. Can we stick to the proposed patch,
> please?
> 
> If we really do care about processes sharing mm _that_much_ then it
> should be handled in the separate patch.

I do care. The OOM reaper cannot work unless SIGKILL is sent to a thread
which is holding mmap_sem for write. Thus, sending SIGKILL to all thread
groups sharing the mm is needed by your down_write_killable(&mm->mmap_sem)
changes. Like I wrote at
http://lkml.kernel.org/r/201604092300.BDI39040.FFSQLJOMHOOVtF@I-love.SAKURA.ne.jp ,
we cannot fix that problem unless you accept the slowpath.

I don't like you don't explain your approach for handling the slowpath.
If you explain your approach for handling the slowpath and I agree on
your approach, I will also agree on the proposed patches.

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