From: Andrew Morton <akpm@linux-foundation.org>
To: Stanislav Kinsburskii <skinsburskii@gmail.com>
Cc: airlied@gmail.com, akhilesh@ee.iitb.ac.in, corbet@lwn.net,
dakr@kernel.org, david@kernel.org, decui@microsoft.com,
haiyangz@microsoft.com, jgg@ziepe.ca, 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: Fri, 10 Jul 2026 22:46:06 -0700 [thread overview]
Message-ID: <20260710224606.69235ab5c49b5987fd33e924@linux-foundation.org> (raw)
In-Reply-To: <alG1JwgUK44dCiN4@skinsburskii>
On Fri, 10 Jul 2026 20:14:47 -0700 Stanislav Kinsburskii <skinsburskii@gmail.com> 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?
>
> Yes, looks like it might.
> What can be done to prevent this?
Well the best way is remove the polling loop and use a proper sleep/wakeup
mechanism - mutex_lock()/prepare_to_wait()/etc.
If the polling loop is to be retained then maybe msleep(1) or
usleep_range()?
next prev parent reply other threads:[~2026-07-11 5:46 UTC|newest]
Thread overview: 23+ 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 [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
2026-07-10 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
2026-07-10 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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