From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: "Michal Hocko" <mhocko@kernel.org>,
"Christian König" <christian.koenig@amd.com>
Cc: kvm@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
"Tetsuo Handa" <penguin-kernel@I-love.SAKURA.ne.jp>,
"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
"Sudeep Dutt" <sudeep.dutt@intel.com>,
dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
"Andrea Arcangeli" <aarcange@redhat.com>,
"David (ChunMing) Zhou" <David1.Zhou@amd.com>,
"Dimitri Sivanich" <sivanich@sgi.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org,
"David Airlie" <airlied@linux.ie>,
"Doug Ledford" <dledford@redhat.com>,
"David Rientjes" <rientjes@google.com>,
xen-devel@lists.xenproject.org, intel-gfx@lists.freedesktop.org,
"Jani Nikula" <jani.nikula@linux.intel.com>,
"Leon Romanovsky" <leonro@mellanox.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Juergen Gross" <jgross@suse.com>,
"Mike Marciniszyn" <mike.marciniszyn@intel.com>,
"Dennis Dalessandro" <dennis.dalessandro@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
"Ashutosh Dixit" <ashutosh.dixit@intel.com>,
"Alex Deucher" <alexander.deucher@amd.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Felix Kuehling" <felix.kuehling@amd.com>
Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers
Date: Fri, 24 Aug 2018 15:10:08 +0200 [thread overview]
Message-ID: <23d071d2-82e4-9b78-1000-be44db5f6523@gmail.com> (raw)
In-Reply-To: <20180824130132.GP29735@dhcp22.suse.cz>
Am 24.08.2018 um 15:01 schrieb Michal Hocko:
> On Fri 24-08-18 14:52:26, Christian König wrote:
>> Am 24.08.2018 um 14:33 schrieb Michal Hocko:
> [...]
>>> Thiking about it some more, I can imagine that a notifier callback which
>>> performs an allocation might trigger a memory reclaim and that in turn
>>> might trigger a notifier to be invoked and recurse. But notifier
>>> shouldn't really allocate memory. They are called from deep MM code
>>> paths and this would be extremely deadlock prone. Maybe Jerome can come
>>> up some more realistic scenario. If not then I would propose to simplify
>>> the locking here. We have lockdep to catch self deadlocks and it is
>>> always better to handle a specific issue rather than having a code
>>> without a clear indication how it can recurse.
>> Well I agree that we should probably fix that, but I have some concerns to
>> remove the existing workaround.
>>
>> See we added that to get rid of a real problem in a customer environment and
>> I don't want to that to show up again.
> It would really help to know more about that case and fix it properly
> rather than workaround it like this. Anyway, let me think how to handle
> the non-blocking notifier invocation then. I was not able to come up
> with anything remotely sane yet.
With avoiding allocating memory in the write lock path I don't see an
issue any more with that.
All what the write lock path does now is adding items to a linked lists,
arrays etc....
So there is no more blocking involved here and the read lock side should
be able to grab the lock immediately.
Christian.
next prev parent reply other threads:[~2018-08-24 13:10 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 [this message]
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
2018-08-24 14:40 ` Jerome Glisse
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