From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Xu <peterx@redhat.com>
Cc: Guo Ren <guoren@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-csky@vger.kernel.org
Subject: Re: [PATCH 07/25] mm/csky: Use mm_fault_accounting()
Date: Wed, 17 Jun 2020 10:53:23 -0700 [thread overview]
Message-ID: <CAHk-=wi=58J7d5iyFyYyHrU+pzjWB55cit_LQCkSkavpH-trsg@mail.gmail.com> (raw)
In-Reply-To: <20200617154925.GC76766@xz-x1>
On Wed, Jun 17, 2020 at 8:49 AM Peter Xu <peterx@redhat.com> wrote:
>
> I don't think it's a must, but mmap_sem should not be required at least by
> observing current code. E.g., do_user_addr_fault() of x86 does the accounting
> without mmap_sem even before this series.
All the accounting should be per-thread and not need any locking.
Which is why a remote GUP should never account to the remote mm - not
only isn't there an unambiguous thread to account to (an mm can share
many threads), but it would require locking not just for the remote
update, but for all normal page faults.
Linus
next prev parent reply other threads:[~2020-06-17 17:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200615221607.7764-1-peterx@redhat.com>
2020-06-15 22:15 ` [PATCH 07/25] mm/csky: Use mm_fault_accounting() Peter Xu
2020-06-17 7:04 ` Guo Ren
2020-06-17 15:49 ` Peter Xu
2020-06-17 17:53 ` Linus Torvalds [this message]
2020-06-17 19:58 ` Peter Xu
2020-06-17 20:15 ` Linus Torvalds
2020-06-18 14:38 ` Peter Xu
2020-06-18 17:15 ` Linus Torvalds
2020-06-18 21:24 ` Peter Xu
2020-06-18 22:28 ` Peter Xu
2020-06-18 22:59 ` Linus Torvalds
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