Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 2 Nov 2020 14:39:49 -0800 | Subject | Re: [PATCH v2 0/2] Add a seqcount between gup_fast and copy_page_range() |
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On Mon, Nov 2, 2020 at 2:19 PM Ahmed S. Darwish <a.darwish@linutronix.de> wrote: > > Disabling preemption for seqcount_t write-side critical sections was > never a new requirement. It has always been this way, for the reasons > explained at Documentation/locking/seqlock.rst, "Introduction" section.
Note that that is only true if you spin on the reading side (either of the two kinds of spinning: (a) spinning to wait for it to become even, or (b) repeating if they don't match)
Which this code doesn't do, it just fails.
I'm not sure how to perhaps document that.
Linus
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