From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: "Jérôme Glisse" <jglisse@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, "David (ChunMing) Zhou" <David1.Zhou@amd.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Alex Deucher" <alexander.deucher@amd.com>,
"David Airlie" <airlied@linux.ie>,
"Jani Nikula" <jani.nikula@linux.intel.com>,
"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
"Doug Ledford" <dledford@redhat.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Mike Marciniszyn" <mike.marciniszyn@intel.com>,
"Dennis Dalessandro" <dennis.dalessandro@intel.com>,
"Sudeep Dutt" <sudeep.dutt@intel.com>,
"Ashutosh Dixit" <ashutosh.dixit@intel.com>,
"Dimitri Sivanich" <sivanich@sgi.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Juergen Gross" <jgross@suse.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Felix Kuehling" <felix.kuehling@amd.com>,
kvm@vger.kernel.org, amd-gfx@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
linux-rdma@vger.kernel.org, xen-devel@lists.xenproject.org,
"Christian König" <christian.koenig@amd.com>,
"David Rientjes" <rientjes@google.com>,
"Leon Romanovsky" <leonro@mellanox.com>
Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers
Date: Fri, 24 Aug 2018 18:38:53 +0200 [thread overview]
Message-ID: <20180824163853.GV29735@dhcp22.suse.cz> (raw)
In-Reply-To: <72844762-7398-c770-1702-f945573f4059@i-love.sakura.ne.jp>
On Fri 24-08-18 23:52:25, Tetsuo Handa wrote:
> On 2018/08/24 22:32, Michal Hocko wrote:
> > On Fri 24-08-18 22:02:23, Tetsuo Handa wrote:
> >> I worry that (currently
> >> out-of-tree) users of this API are involving work / recursion.
> >
> > I do not give a slightest about out-of-tree modules. They will have to
> > accomodate to the new API. I have no problems to extend the
> > documentation and be explicit about this expectation.
>
> You don't need to care about out-of-tree modules. But you need to hear from
> mm/hmm.c authors/maintainers when making changes for mmu-notifiers.
>
> > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> > index 133ba78820ee..698e371aafe3 100644
> > --- a/include/linux/mmu_notifier.h
> > +++ b/include/linux/mmu_notifier.h
> > @@ -153,7 +153,9 @@ struct mmu_notifier_ops {
> > *
> > * If blockable argument is set to false then the callback cannot
> > * sleep and has to return with -EAGAIN. 0 should be returned
> > - * otherwise.
> > + * otherwise. Please note that if invalidate_range_start approves
> > + * a non-blocking behavior then the same applies to
> > + * invalidate_range_end.
>
> Prior to 93065ac753e44438 ("mm, oom: distinguish blockable mode for mmu
> notifiers"), whether to utilize MMU_INVALIDATE_DOES_NOT_BLOCK was up to
> mmu-notifiers users.
>
> - * If both of these callbacks cannot block, and invalidate_range
> - * cannot block, mmu_notifier_ops.flags should have
> - * MMU_INVALIDATE_DOES_NOT_BLOCK set.
> + * If blockable argument is set to false then the callback cannot
> + * sleep and has to return with -EAGAIN. 0 should be returned
> + * otherwise.
>
> Even out-of-tree mmu-notifiers users had rights not to accommodate (i.e.
> make changes) immediately by not setting MMU_INVALIDATE_DOES_NOT_BLOCK.
>
> Now we are in a merge window. And we noticed a possibility that out-of-tree
> mmu-notifiers users might have trouble with making changes immediately in order
> to follow 93065ac753e44438 if expectation for mm/hmm.c changes immediately.
> And you are trying to ignore such possibility by just updating expected behavior
> description instead of giving out-of-tree users a grace period to check and update
> their code.
This is just ridiculous. I have no idea what you are trying to achieve
here but please read through Documentation/process/stable-api-nonsense.rst
before you try to make strong statements again.
I have changed an in-kernel interface. I have gone through all users and
fixed them up. It is really appreciated to double check after me and I
am willing to fix up any fallouts. But that is just about it. I do not
get a whit about _any_ out of tree drivers when changing the interface.
I am willing to answer any questions regarding this change so developers
of those drivers know how to do their change properly but doing so is
completely their business.
> >> and keeps "all operations protected by hmm->mirrors_sem held for write are
> >> atomic". This suggests that "some operations protected by hmm->mirrors_sem held
> >> for read will sleep (and in the worst case involves memory allocation
> >> dependency)".
> >
> > Yes and so what? The clear expectation is that neither of the range
> > notifiers do not sleep in !blocking mode. I really fail to see what you
> > are trying to say.
>
> I'm saying "Get ACK from Jérôme about mm/hmm.c changes".
HMM is a library layer for other driver, until those get merged the same
applies for them as well.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-08-24 16:39 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 11:50 [PATCH] mm, oom: distinguish blockable mode for mmu notifiers Michal Hocko
2018-07-16 23:12 ` Andrew Morton
2018-07-17 4:03 ` Leon Romanovsky
2018-07-17 8:12 ` Michal Hocko
2018-07-20 23:01 ` Andrew Morton
2018-07-23 8:43 ` Michal Hocko
2018-07-19 9:12 ` Michal Hocko
2018-07-21 0:09 ` Andrew Morton
2018-07-23 7:03 ` Michal Hocko
2018-07-23 7:11 ` Michal Hocko
2018-07-23 8:11 ` Michal Hocko
2018-07-24 14:17 ` Michal Hocko
2018-07-24 19:53 ` Andrew Morton
2018-07-25 6:17 ` Michal Hocko
2018-07-24 21:07 ` David Rientjes
2018-07-25 6:13 ` Michal Hocko
2018-08-24 10:54 ` Tetsuo Handa
2018-08-24 11:32 ` Michal Hocko
2018-08-24 11:43 ` Christian König
2018-08-24 11:52 ` Michal Hocko
2018-08-24 11:57 ` Christian König
2018-08-24 12:03 ` Michal Hocko
2018-08-24 12:18 ` Christian König
2018-08-24 12:33 ` Michal Hocko
2018-08-24 12:52 ` Christian König
2018-08-24 13:01 ` Michal Hocko
2018-08-24 13:10 ` Christian König
2018-08-24 13:24 ` Michal Hocko
2018-08-24 13:28 ` Christian König
2018-08-24 13:40 ` Michal Hocko
2018-08-24 13:44 ` Christian König
2018-08-24 13:52 ` Michal Hocko
2018-08-26 8:40 ` Tetsuo Handa
2018-08-27 7:41 ` Christian König
2018-09-06 22:46 ` Tetsuo Handa
2018-08-24 15:08 ` Jerome Glisse
2018-08-24 11:36 ` Michal Hocko
2018-08-24 13:02 ` Tetsuo Handa
2018-08-24 13:32 ` Michal Hocko
2018-08-24 14:52 ` Tetsuo Handa
2018-08-24 15:12 ` Jerome Glisse
2018-08-24 16:40 ` Michal Hocko
2018-08-24 17:33 ` Jerome Glisse
2018-08-24 16:38 ` Michal Hocko [this message]
2018-08-24 14:40 ` Jerome Glisse
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