On Mon, May 01, 2017 at 08:33:45PM +0200, Michael Kerrisk (man-pages) wrote: > Hi Mike, > > 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 > missing? I've copied both from Documentation/vm/userfaulftfd.txt, and there we also talk about possibility of addition of synchronous events delivery and that makes the paragraph above to seem crippled :) The major point here is that current events delivery model could be problematic for multi-threaded monitor. I even suspect that it would be impossible to ensure synchronization between page faults and non-page fault events in multi-threaded monitor. > > + > > .\" 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 > > > > Cheers, > > Michael > > > > -- > Michael Kerrisk > Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ > Linux/UNIX System Programming Training: http://man7.org/training/ > -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
