linux-kernel - Re: [RFC PATCH] binder: Don't require the binder lock when killed in binder_thread

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Message-ID: <CAD=FV=X-EPfBLE3oQH1p1OwKrHNPzw+R10nk8poJD-GL=itzSQ@mail.gmail.com>
Date:   Sat, 1 Apr 2017 19:34:53 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     arve@...roid.com, riandrews@...roid.com,
        Todd Kjos <tkjos@...gle.com>, devel@...verdev.osuosl.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [RFC PATCH] binder: Don't require the binder lock when killed in binder_thread_read()

Hi,

On Fri, Mar 31, 2017 at 11:48 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Fri, Mar 31, 2017 at 02:00:13PM -0700, Doug Anderson wrote:
>> On Fri, Mar 31, 2017 at 12:29 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> BTW: I presume that nobody has decided that it would be a wise idea to
>> pick the OOM reaper code back to any stable trees?  It seemed a bit
>> too scary to me, so I wrote a dumber (but easier to backport) solution
>> that avoided the deadlocks I was seeing.  http://crosreview.com/465189
>> and the 3 patches above it in case anyone else stumbles on this thread
>> and is curious.
>
> What specific upstream OOM patches are you referring to?  I'm always
> glad to review patches for stable kernels, just email
> stable@...r.kernel.org the git commit ids and we can take it from there.

+stable

I was wondering about the concept of porting the OOM Reaper back to
older kernels.  The OOM reaper was originally introduced in:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/mm/oom_kill.c?id=aac453635549699c13a84ea1456d5b0e574ef855

Basically the problem described in that patch exists in many older
kernels and I've certainly seen crashes related to this in 3.10, but I
believe older kernels see the same problems too.

Personally I wouldn't know exactly which patches were important to
backport and how far to go.  One could arbitrarily try to backport up
to 4.6.7 (since 4.6 was the first kernel to really have the OOM
reaper) and ignore all the reaper fixes that landed since then.  This
would probably be doable for kernel 4.4, though if anyone was trying
to support older kernels it might get harder.

-Doug