From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
To: Peter Xu <peterx@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.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>,
John Hubbard <jhubbard@nvidia.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: Tue, 3 Nov 2020 01:33:46 +0100 [thread overview]
Message-ID: <20201103003346.GC52235@lx-t490> (raw)
In-Reply-To: <20201031152605.GD6357@xz-x1>
On Sat, Oct 31, 2020 at 11:26:05AM -0400, Peter Xu wrote:
...
> Shall we document this explicitly (if this patch still needs a repost)?
Yes, this patch series needs a v3 :)
> Seems not straightforward since that seems not the usual way to use seqcount,
> not sure whether I'm the only one that feels this way, though.
Yes, this usage is correct but not common. I've proposed a more explicit
comment above the write section code, in my reply to patch #2.
...
> The other thing is, considering this use of seqcount seems to be quite special
> as explained below, I'm just not sure whether this would confuse lockdep or
> kcsan, etc., if we decide to use write_seqcount_t_begin().
>
Lockdep won't be confused as it's not used in the raw_*() variant of the
seqcount APIs.
AFAIK KCSAN also has some margin to protect itself from this: see
seqlock.h KCSAN_SEQLOCK_REGION_MAX.
Thanks,
> Peter Xu
Ahmed Darwish
Linutronix GmbH
next prev parent reply other threads:[~2020-11-03 0:33 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0-v2-dfe9ecdb6c74+2066-gup_fork_jgg@nvidia.com>
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
2020-11-02 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 23:18 ` Ahmed S. Darwish
[not found] ` <2-v2-dfe9ecdb6c74+2066-gup_fork_jgg@nvidia.com>
2020-10-30 16:51 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Jan Kara
[not found] ` <20201030170226.GF2620339@nvidia.com>
2020-11-02 8:31 ` Jan Kara
2020-10-30 22:52 ` Peter Xu
[not found] ` <20201030235121.GQ2620339@nvidia.com>
2020-10-31 15:26 ` Peter Xu
2020-11-03 0:33 ` Ahmed S. Darwish [this message]
2020-11-03 0:17 ` Ahmed S. Darwish
[not found] ` <20201103002532.GL2620339@nvidia.com>
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 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
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
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