From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc: John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>, Peter Xu <peterx@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Christoph Hellwig <hch@lst.de>, Hugh Dickins <hughd@google.com>,
Jan Kara <jack@suse.cz>, Jann Horn <jannh@google.com>,
Kirill Shutemov <kirill@shutemov.name>,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Leon Romanovsky <leonro@nvidia.com>,
Linux-MM <linux-mm@kvack.org>, Michal Hocko <mhocko@suse.com>,
Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork
Date: Wed, 4 Nov 2020 10:38:57 -0800 [thread overview]
Message-ID: <CAHk-=wikhGExmprXgaW+MVXG1zsGpztBbVwOb23vetk41EtTBQ@mail.gmail.com> (raw)
In-Reply-To: <20201104031711.GA227990@lx-t490>
On Tue, Nov 3, 2020 at 7:17 PM Ahmed S. Darwish <a.darwish@linutronix.de> wrote:
>
> Nonetheless, as you mentioned in the later (dropped) part of your
> message, I think do_ is better than __do_, so the final result will be:
>
> do___read_seqcount_retry()
> do_read_seqcount_retry()
> do_raw_write_seqcount_begin()
> do_raw_write_seqcount_end()
> do_write_seqcount_begin()
> ...
>
> and so on.
Looks reasonable to me.
And can you add a few comments to the magic type macros, so that it's
a lot more obvious what the end result was. I clearly wasn't able to
follow all the _Generic() cases from the seqcount_t to the final end
result. It's a really odd combination of subtle _GENERIC() macro and
token pasting to get from zeqcount_t to "false" in
__seqcount_lock_preemptible().
I can see it when I really look, but when looking at the actual use,
it's very non-obvious indeed.
Linus
next prev parent reply other threads:[~2020-11-04 18:46 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-30 14:46 [PATCH v2 0/2] Add a seqcount between gup_fast and copy_page_range() Jason Gunthorpe
2020-10-30 14:46 ` [PATCH v2 1/2] mm: reorganize internal_get_user_pages_fast() Jason Gunthorpe
2020-10-30 16:29 ` Jan Kara
2020-10-30 21:31 ` John Hubbard
2020-10-30 22:36 ` Peter Xu
2020-10-30 14:46 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Jason Gunthorpe
2020-10-30 16:51 ` Jan Kara
2020-10-30 17:02 ` Jason Gunthorpe
2020-11-02 8:31 ` Jan Kara
2020-10-30 21:20 ` John Hubbard
2020-10-30 22:52 ` Peter Xu
2020-10-30 23:51 ` Jason Gunthorpe
2020-10-31 15:26 ` Peter Xu
2020-11-03 0:33 ` Ahmed S. Darwish
2020-11-03 0:17 ` Ahmed S. Darwish
2020-11-03 0:25 ` Jason Gunthorpe
2020-11-03 0:41 ` Ahmed S. Darwish
2020-11-03 2:20 ` John Hubbard
2020-11-03 6:52 ` Ahmed S. Darwish
2020-11-03 7:05 ` John Hubbard
2020-11-03 17:40 ` Linus Torvalds
2020-11-03 17:40 ` Linus Torvalds
2020-11-04 1:32 ` Ahmed S. Darwish
2020-11-04 2:01 ` John Hubbard
2020-11-04 3:17 ` Ahmed S. Darwish
2020-11-04 18:38 ` Linus Torvalds [this message]
2020-11-04 18:38 ` Linus Torvalds
2020-11-04 19:54 ` Ahmed S. Darwish
2020-12-09 18:38 ` [tip: locking/core] seqlock: Prefix internal seqcount_t-only macros with a "do_" tip-bot2 for Ahmed S. Darwish
2020-12-09 18:38 ` [tip: locking/core] seqlock: kernel-doc: Specify when preemption is automatically altered tip-bot2 for Ahmed S. Darwish
2020-11-10 11:53 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Peter Zijlstra
2020-12-03 10:35 ` [tip: locking/core] seqlock: Rename __seqprop() users tip-bot2 for Peter Zijlstra
2020-11-03 17:03 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Peter Xu
2020-11-02 23:58 ` Ahmed S. Darwish
2020-11-02 22:19 ` [PATCH v2 0/2] Add a seqcount between gup_fast and copy_page_range() Ahmed S. Darwish
2020-11-02 22:39 ` Linus Torvalds
2020-11-02 22:39 ` Linus Torvalds
2020-11-02 23:18 ` Ahmed S. Darwish
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