Re: [PATCH man-pages 4/5] userfaultfd.2: add note about asynchronios events delivery
From: Michael Kerrisk (man-pages)
Date: Mon May 01 2017 - 14:33:55 EST
On 05/01/2017 07:43 AM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Thanks. Applied. One question below.
> man2/userfaultfd.2 | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
> diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
> index 8b89162..f177bba 100644
> --- a/man2/userfaultfd.2
> +++ b/man2/userfaultfd.2
> @@ -112,6 +112,18 @@ created for the child process,
> which allows userfaultfd monitor to perform user-space paging
> for the child process.
> +Unlike page faults which have to be synchronous and require
> +explicit or implicit wakeup,
> +all other events are delivered asynchronously and
> +the non-cooperative process resumes execution as
> +soon as manager executes
> +.BR read(2).
> +The userfaultfd manager should carefully synchronize calls
> +to UFFDIO_COPY with the events processing.
> +The current asynchronous model of the event delivery is optimal for
> +single threaded non-cooperative userfaultfd manager implementations.
The preceding paragraph feels incomplete. It seems like you want to make
a point with that last sentence, but the point is not explicit. What's
> .\" FIXME elaborate about non-cooperating mode, describe its limitations
> .\" for kernels before 4.11, features added in 4.11
> .\" and limitations remaining in 4.11
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/