Re: [patch] voluntary-preempt-2.6.8.1-P0

Lee Revell
2004-08-15T23:23:53Z

On Sun, 2004-08-15 at 07:56, Ingo Molnar wrote:
> i've uploaded the -P0 patch:
>
> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.8.1-P0
>
> those who had APIC (and USB, under SMP) problems under previous
> versions, are the problems still present in -P0?
>
> Changes:
>

The ide and /dev/random related latencies are indeed gone. Here is an
ugly one that I got:

preemption latency trace v1.0
-----------------------------
latency: 142 us, entries: 4 (4)
process: ksoftirqd/0/2, uid: 0
nice: -10, policy: 0, rt_priority: 0
=======>
0.000ms (+0.000ms): rhine_check_duplex (rhine_timer)
0.000ms (+0.000ms): mdio_read (rhine_check_duplex)
0.067ms (+0.067ms): mdio_read (rhine_timer)
0.139ms (+0.071ms): check_preempt_timing (sub_preempt_count)

This looks like the exact same problem Florian had, in his case it was
the sis900 driver. Your recommendation was:

#define mdio_delay() do { } while (0)

Should I try this?

Also, isn't there a better solution than for network drivers to actively
poll for changes in link status? Can't they just register a callback that
will get run on a link state change event?

Lee