From: Alexander Gordeev <agordeev@linux.ibm.com>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Lorenzo Stoakes <ljs@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Oscar Salvador <osalvador@suse.de>,
linux-s390@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>
Subject: Re: [PATCH v2] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access
Date: Thu, 7 May 2026 12:32:09 +0200 [thread overview]
Message-ID: <43815634-29d3-4fa4-b967-0e251ff32f73-agordeev@linux.ibm.com> (raw)
In-Reply-To: <20260507093433.q5xybwumryxclnqy@master>
On Thu, May 07, 2026 at 09:34:33AM +0000, Wei Yang wrote:
> >@@ -310,7 +310,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
> > goto restart;
> > }
> > pvmw->pte++;
> >- } while (pte_none(ptep_get(pvmw->pte)));
> >+ } while (pte_none(ptep_get_lockless(pvmw->pte)));
>
> As Oscar mentioned in lkml.org/lkml/2026/4/27/630, map_pte() may take the
> lock. So probably it is not right?
If I read the code correctly map_pte() might take the lock, but also
might not take it. If it took the lock and uses ptep_get_lockless(),
then it is fine. But if it did not take the lock and uses ptep_get(),
then it is an issue.
> >
> > if (!pvmw->ptl) {
> > spin_lock(ptl);
> >--
> >2.51.0
> >
>
> --
> Wei Yang
Thanks!
next prev parent reply other threads:[~2026-05-07 10:32 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-04 13:04 [PATCH v2] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access Alexander Gordeev
2026-05-07 9:34 ` Wei Yang
2026-05-07 10:32 ` Alexander Gordeev [this message]
2026-05-08 1:00 ` Wei Yang
2026-05-08 5:15 ` Alexander Gordeev
2026-05-08 6:23 ` Wei Yang
2026-05-08 8:17 ` David Hildenbrand (Arm)
2026-05-08 8:34 ` Alexander Gordeev
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