| From | David Howells <> | Subject | Re: [PATCH 04/11] General notification queue with user mmap()'able ring buffer [ver #7] | Date | Tue, 03 Sep 2019 17:06:37 +0100 |
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Hillf Danton <hdanton@sina.com> wrote:
> > + smp_store_release(&buf->meta.head, head); > > Add a line of comment for the paring smp_load_acquire(). > I did not find it in 04/11.
You won't find smp_load_acquire() - it's not in the kernel, though if you look in the sample, you'll find the corresponding barrier in userspace. Note that there's a further implicit barrier you don't see.
I've added the comments:
/* Barrier against userspace, ordering data read before tail read */ ring_tail = READ_ONCE(buf->meta.tail);
and:
/* Barrier against userspace, ordering head update after data write. */ smp_store_release(&buf->meta.head, head);
David
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