Re: [PATCH v2 1/3] seqlock: add raw_seqcount_try_begin

[David Hildenbrand]

On 22.11.24 12:19, Peter Zijlstra wrote:
> On Fri, Nov 22, 2024 at 12:10:29PM +0100, David Hildenbrand wrote:
>
> > In gup_fast(), we simply do
> >
> > seq = raw_read_seqcount(&current->mm->write_protect_seq);
> > if (seq & 1)
> > 	return 0;
> >
> > Should we be using that there as well?
> >
> > if (!raw_seqcount_try_begin(&current->mm->write_protect_seqs, seq))
> > 	return 0;
>
> Might as well. A quick grep doesn't find me another instance of this
> pattern, but does find me something 'funny' in net/netfilter/x_tables.c.
> Let's pretend I didn't see that for now ... *sigh*

:)

I'm also not 100% sure about barriers in gup_fast() around the 
raw_seqcount .... and I'm pretending I didn't see any of that as well ...

> Want me to stick a patch like this on, or do you want to do that later,
> when the dust has settled?

Feel free to add a patch to just change that as well, it's an easy change.

For this patch

Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb