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    SubjectRe: [PATCH] input: evdev: Use multi-reader buffer to save space (rev5)
    On Wed, Jun 23, 2010 at 10:11:47AM +0200, Henrik Rydberg wrote:
    > Dmitry Torokhov wrote:
    >
    > > Overall I am starting getting concerned about proper isolation between
    > > clients. Right now, if one client stops reading events and another one
    > > issues grab then the first client will only get events that were
    > > accumulated before grab tookm place. With the new shared buffer the
    > > first client may get "grabbed" events if it stop for long enough for
    > > buffer to wrap around.
    >
    > Doing some research, the semantics of ioctl have obviously been discussed
    > before, and I believe this points to another such issue. When grabbing a device,
    > are we guaranteeing that the device no longer sends events to other clients, or
    > are we guaranteeing that other clients can no longer read the device? If the
    > latter, clearing all client buffers in conjunction with a grab would be
    > appropriate, and would solve this issue.


    Yes, I think it would be acceptable approach.

    >
    > > Do we really same that much memory here? We normally do not have that
    > > many users connected to event devices at once...
    >
    > Ok, let's scratch this. Although I think the idea of multi-reader buffers is
    > sound, it is obviously sufficiently incompatible with the current approach to
    > produce distastefully complex patches. I will return with a new set which only
    > fixes the buffer resize problem, and leaves the rest for later.
    >

    Right, let's merge this and also MT slots and revisit this issue at some
    later point.

    Thanks.

    --
    Dmitry


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