From: Jason Gunthorpe <jgg@ziepe.ca>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Stanislav Kinsburskii <skinsburskii@gmail.com>,
airlied@gmail.com, akhilesh@ee.iitb.ac.in, corbet@lwn.net,
dakr@kernel.org, david@kernel.org, decui@microsoft.com,
haiyangz@microsoft.com, kees@kernel.org, kys@microsoft.com,
leon@kernel.org, liam@infradead.org, lizhi.hou@amd.com,
ljs@kernel.org, longli@microsoft.com, lyude@redhat.com,
maarten.lankhorst@linux.intel.com, mamin506@gmail.com,
mhocko@suse.com, mripard@kernel.org,
nouveau@lists.freedesktop.org, ogabbay@kernel.org,
oleg@redhat.com, rppt@kernel.org, shuah@kernel.org,
simona@ffwll.ch, skhan@linuxfoundation.org, surenb@google.com,
tzimmermann@suse.de, vbabka@kernel.org, wei.liu@kernel.org,
dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-rdma@vger.kernel.org
Subject: Re: [PATCH v8 4/8] mshv: Use hmm_range_fault_unlocked_timeout() for region faults
Date: Mon, 13 Jul 2026 11:55:03 -0300 [thread overview]
Message-ID: <20260713145503.GC3133966@ziepe.ca> (raw)
In-Reply-To: <20260710151216.0397a6f9ac5c7b4ccd274cc1@linux-foundation.org>
On Fri, Jul 10, 2026 at 03:12:16PM -0700, Andrew Morton wrote:
> > + mutex_lock(®ion->mreg_mutex);
> > +
> > + if (mmu_interval_read_retry(range.notifier, range.notifier_seq)) {
> > + mutex_unlock(®ion->mreg_mutex);
> > + cond_resched();
> > + goto again;
> > + }
> > +
>
> If the calling process has realtime scheduling policy and either a)
> we're uniprocessor or b) this process and the holder of
> interval_sub->invalidate_seq are both pinned to the same CPU then
> cond_resched() won't do anything, and this might be an infinite loop?
I think hmm and kvm have had this issue for a long time? I don't see
anything in the mmu notifier locking scheme that would alleviate it at
least
So.. In terms of this series I'd leave it, it is no worse than before?
Jason
next prev parent reply other threads:[~2026-07-13 14:55 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-10 21:26 [PATCH v8 0/8] mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings Stanislav Kinsburskii
2026-07-10 21:26 ` [PATCH v8 1/8] mm/hmm: move page fault handling out of walk callbacks Stanislav Kinsburskii
2026-07-10 21:26 ` [PATCH v8 2/8] mm/hmm: add hmm_range_fault_unlocked_timeout() for mmap lock-drop support Stanislav Kinsburskii
2026-07-10 22:12 ` Andrew Morton
2026-07-11 3:09 ` Stanislav Kinsburskii
2026-07-10 21:26 ` [PATCH v8 3/8] selftests/mm: add HMM test for mmap lock-dropping faults Stanislav Kinsburskii
2026-07-10 21:26 ` [PATCH v8 4/8] mshv: Use hmm_range_fault_unlocked_timeout() for region faults Stanislav Kinsburskii
2026-07-10 22:12 ` Andrew Morton
2026-07-11 3:14 ` Stanislav Kinsburskii
2026-07-11 5:46 ` Andrew Morton
2026-07-13 16:56 ` Stanislav Kinsburskii
2026-07-13 14:55 ` Jason Gunthorpe [this message]
2026-07-10 21:26 ` [PATCH v8 5/8] drm/nouveau: Use hmm_range_fault_unlocked_timeout() for SVM faults Stanislav Kinsburskii
2026-07-10 22:12 ` Andrew Morton
2026-07-11 3:16 ` Stanislav Kinsburskii
2026-07-11 5:48 ` Andrew Morton
2026-07-13 16:59 ` Stanislav Kinsburskii
2026-07-10 21:27 ` [PATCH v8 6/8] RDMA/umem: Use hmm_range_fault_unlocked_timeout() for ODP faults Stanislav Kinsburskii
2026-07-10 21:27 ` [PATCH v8 7/8] accel/amdxdna: Use hmm_range_fault_unlocked_timeout() for range population Stanislav Kinsburskii
2026-07-10 22:12 ` Andrew Morton
2026-07-11 3:19 ` Stanislav Kinsburskii
2026-07-10 21:27 ` [PATCH v8 8/8] drm/gpusvm: Use hmm_range_fault_unlocked_timeout() for range faults Stanislav Kinsburskii
2026-07-10 22:12 ` Andrew Morton
2026-07-13 16:30 ` Matthew Brost
2026-07-13 17:01 ` Stanislav Kinsburskii
2026-07-10 22:11 ` [PATCH v8 0/8] mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings Andrew Morton
2026-07-11 3:22 ` Stanislav Kinsburskii
2026-07-11 5:49 ` Andrew Morton
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