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SubjectRe: setitimer lowlatency-2.2.13-A1 questions

On Mon, 6 Dec 1999, William Montgomery wrote:

> I tried using setitimer as a scheduling source for lowlatency testing
> with generally good results. I left my test running over the weekend
> and found some large latencies had occurred. It appears that since
> the signal generation occurs in timer_bh, it is possible for a user
> task to run between when the timer_interrupt occurs and when timer_bh
> runs (~2msec in my case).

that should not be possible (except on SMP where there might be a window).
You are not running SMP, right? The TIMER_BH is run right when the IRQ
handler returns to non-irq context (which might be user-space or kernel
space), so it's not possible to 'lose' a TIMER_BH event due to some task
running. BHs might get delayed due to interrupts though, so you might want
to profile how long various interrupt sources execute.

-- mingo


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