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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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