Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

[Ingo Molnar]

* Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> The sound subsystem uses a lot of sleep_on() variants. We know that
> they are racy. Might this be related ?

i doubt it is related - sleep_on() is mostly racy on SMP and Rui is
doing UP tests. Also, for a sleep_on() race to occur you'd have to race
with the wakeup - but in the Jackd case that is highly unlikely because
it sleeps well before the next interrupt is due. So while a sleep_on()
race could in theory make _existing_ latencies worse, it cannot by
itself introduce the first latency.

but now it should be possible to prove that Jackd itself doesnt
introduce latencies, via the userspace-atomicity mode feature in -V0.5.5
:-) If that proves that the latencies dont occur in Jackd (and if it's
not another, even higher prio thread that causes the delay) then we can
pass the ball back to the kernel.

	Ingo
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