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    SubjectRe: [PATCH] Limit number of concurrent hotplug processes
    Andrew wrote:
    > We'd allocate the same amount of memory if we were sending
    > messages up a socket/pipe to userspace, which is what we should always have
    > done, instead of the direct-exec - it's caused tons of trouble.

    This touches on a question I have, off-topic to the discussion of
    the patch proposed by Hannes.

    Doesn't doing a direct-exec have one powerful advantage over sending
    some message or kevent to userspace by socket/pipe/d-bus, in that
    sending the message requires that there is some userspace code already
    running that is competent to receive the message?

    Doing the usermodehelper direct-exec _both_ provides the thread context
    in which to execute, _and_ the code to be executed. The alternative
    seems to require long running threads, primed and ready to accept
    particular events, cluttering up the system.

    I will readily grant that this usermodehelper direct kernel exec thing
    seems weird as all heck to me. But I predict that in a couple of weeks
    lkml will be seeing a patch from me (the next version of the 'cpuset'
    patch I'm working with Simon and Sylvain of Bull) using it -- because
    the alternative of a long running, rarely used, user thread just for one
    obscure particular event that required user code sucked worse.

    Am I missing something? Are there _always_ better solutions than
    usermodehelper's kernel direct-exec?

    Or perhaps am I confusing what Andrew was referring to and the various
    mechanisms available here in unfortunate ways?

    I won't rest till it's the best ...
    Programmer, Linux Scalability
    Paul Jackson <> 1.650.933.1373
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