Messages in this thread | | | Date | Mon, 6 Dec 1999 21:51:31 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: [patch] Re: setitimer lowlatency-2.2.13-A1 questions |
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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 atomicity.
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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