On Mon, Mar 21, 2016 at 08:00:49PM +0900, Tetsuo Handa wrote:

Greg Kroah-Hartman wrote:

quoted

On Tue, Mar 08, 2016 at 03:18:59PM +0100, Michal Hocko wrote:

quoted

On Tue 08-03-16 20:01:32, Tetsuo Handa wrote:

quoted

Currently, lowmemorykiller (LMK) is using TIF_MEMDIE for two purposes.
One is to remember processes killed by LMK, and the other is to
accelerate termination of processes killed by LMK.

But since LMK is invoked as a memory shrinker function, there still
should be some memory available. It is very likely that memory
allocations by processes killed by LMK will succeed without using
ALLOC_NO_WATERMARKS via TIF_MEMDIE. Even if their allocations cannot
escape from memory allocation loop unless they use ALLOC_NO_WATERMARKS,
lowmem_deathpending_timeout can guarantee forward progress by choosing
next victim process.

On the other hand, mark_oom_victim() assumes that it must be called with
oom_lock held and it must not be called after oom_killer_disable() was
called. But LMK is calling it without holding oom_lock and checking
oom_killer_disabled. It is possible that LMK calls mark_oom_victim()
due to allocation requests by kernel threads after current thread
returned from oom_killer_disabled(). This will break synchronization
for PM/suspend.

This patch introduces per a task_struct flag for remembering processes
killed by LMK, and replaces TIF_MEMDIE with that flag. By applying this
patch, assumption by mark_oom_victim() becomes true.

Thanks for looking into this. A separate flag sounds like a better way
to go (assuming that the flags are not scarce which doesn't seem to be
the case here).
 
The LMK cannot kill the frozen tasks now but this shouldn't be a big deal
because this is not strictly necessary for the system to move on. We are
not OOM.

quoted

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michal Hocko <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arve Hjonnevag <arve@android.com>
Cc: Riley Andrews <redacted>

Acked-by: Michal Hocko <mhocko@suse.com>

So, any objection for me taking this through the staging tree?

Seems no objection. Please take this through the staging tree.

Ok, will do so after 4.6-rc1 is out.

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