Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers

From: Christian KÃnig
Date: Fri Aug 24 2018 - 08:19:14 EST

Am 24.08.2018 um 14:03 schrieb Michal Hocko:
On Fri 24-08-18 13:57:52, Christian KÃnig wrote:
Am 24.08.2018 um 13:52 schrieb Michal Hocko:
On Fri 24-08-18 13:43:16, Christian KÃnig wrote:
That won't work like this there might be multiple
invalidate_range_start()/invalidate_range_end() pairs open at the same time.
E.g. the lock might be taken recursively and that is illegal for a
I am not sure I follow. Are you saying that one invalidate_range might
trigger another one from the same path?
No, but what can happen is:


Grabbing the read lock twice would be illegal in this case.
I am sorry but I still do not follow. What is the context the two are
called from?

I don't have the slightest idea.

Can you give me an example. I simply do not see it in the
code, mostly because I am not familiar with it.

I'm neither.

We stumbled over that by pure observation and after discussing the problem with Jerome came up with this solution.

No idea where exactly that case comes from, but I can confirm that it indeed happens.