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    SubjectRe: [patch] Re: setitimer lowlatency-2.2.13-A1 questions

    On Mon, 6 Dec 1999, Manfred Spraul wrote:

    > Is there a special reason why do_bottom_half() calls __sti() and

    for example the timer bh can run for a long time (if there are many timers
    expiring at once), so it's not justified to disable interrupts while
    bottom halves are running. Also, some historic bottom halves wait for
    interrupts to complete by busy-waiting (i think the PC keyboard
    led-setting stuff is such).

    > __cli() directly? This seems wrong, what about using the normal
    > __save_flags()/__sti()/__restore_flags()?

    this does not change the fundamental problem: run_bottom_halves() must not
    be called if interrupts are disabled, because the breaks local-IRQ

    i think in 2.5 (or earlier) we should do a BUG() if enable_bh() is called
    with IRQs disabled - this will sort out the problems and solves the
    latency issue as well.

    -- mingo

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