From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: David Hildenbrand <david@redhat.com>, g@box.shutemov.name
Cc: Jann Horn <jannh@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Zach O'Keefe <zokeefe@google.com>,
linux-kernel@vger.kernel.org, Yang Shi <shy828301@gmail.com>
Subject: Re: [PATCH] mm/khugepaged: Fix ->anon_vma race
Date: Tue, 24 Jan 2023 03:51:02 +0300 [thread overview]
Message-ID: <20230124005102.ow33h7tfmj5eqyr3@box.shutemov.name> (raw)
In-Reply-To: <1b8696ec-e2be-7b7b-705c-e2dcabb2e8e5@redhat.com>
On Mon, Jan 23, 2023 at 12:07:05PM +0100, David Hildenbrand wrote:
> > > commit bedf03416913d88c796288f9dca109a53608c745
> > > Author: Yang Shi <shy828301@gmail.com>
> > > Date: Wed Sep 7 11:01:44 2022 -0700
> > >
> > > powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush
> > > The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will
> > > move to use RCU instead of disabling local interrupts in fast-GUP. Using
> > > an IPI is the old-styled way of serializing against fast-GUP although it
> > > still works as expected now.
> > > And fast-GUP now fixed the potential race with THP collapse by checking
> > > whether PMD is changed or not. So IPI broadcast in radix pmd collapse
> > > flush is not necessary anymore. But it is still needed for hash TLB.
> >
> > Okay. But I think tlb_remove_table_sync_one() belongs inside
> > pmdp_collapse_flush(). Collapsing pmd table into huge page without
> > serialization is a bug. They should not be separate.
>
> Agreed. But I wonder if it should be moved into a generic
> pmdp_collapse_flush(), that calls an arch specific __pmdp_collapse_flush().
Um? There's no __pmdp_collapse_flush(). Architectural code overrides
pmdp_collapse_flush() altogether. It has know how to serialize properly
for the arch.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2023-01-24 0:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-11 13:33 [PATCH] mm/khugepaged: Fix ->anon_vma race Jann Horn
2023-01-12 1:06 ` Yang Shi
2023-01-13 19:36 ` Jann Horn
2023-01-12 8:56 ` Kirill A. Shutemov
2023-01-12 18:12 ` Yang Shi
2023-01-13 0:10 ` Kirill A. Shutemov
2023-01-13 3:22 ` Yang Shi
2023-01-13 19:28 ` Jann Horn
2023-01-15 19:06 ` Kirill A. Shutemov
2023-01-16 12:06 ` Jann Horn
2023-01-16 12:34 ` Kirill A. Shutemov
2023-01-16 12:54 ` Jann Horn
2023-01-16 13:07 ` David Hildenbrand
2023-01-16 13:47 ` Kirill A. Shutemov
2023-01-23 11:07 ` David Hildenbrand
2023-01-24 0:51 ` Kirill A. Shutemov [this message]
2023-01-24 10:19 ` David Hildenbrand
2023-01-17 18:57 ` Yang Shi
2023-01-17 19:12 ` Jann Horn
2023-01-17 22:55 ` Andrew Morton
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