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

Thomas Gleixner
2004-10-29T08:29:20Z

On Fri, 2004-10-29 at 10:02 +0200, Ingo Molnar wrote:
> there are multiple possibilities of how this ~700 usecs delay occured:
>
> - the kernel still has a wakeup bug. But this should be detected by the
> tracer which measures the time between when the task hits the
> runqueue and the task gets to execute on the CPU. Also, if there is a
> critical section in the kernel that is 700 usecs long it would be
> detected by _another_, independent timing/tracing mechanism that
> measures critical sections. The likelyhood of both the scheduler
> _and_ two independent kernel-tracers being buggy in the same way is
> quite significantly low. (not to mention the user-space amlat tool
> which seems to agree with the kernel instrumentation.)
>

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

tglx