Cannot restart jackd without getting XRUN

[CoreDump]

Hello,

I try to use jack audio connection kit, but I have some problem with it.

First I setup my kernel (2.6.15) to use low latency settings, and use realtime-lsm to allow realtime scheduling for users.
I have not made a RT kernel since I do not have strong requirements on latency.
Everything is compiled correctly (jackd-tmpfs etc...), and I use qjackctl for starting jackd.

On the first startup everything is ok using alsa as output, buffer of 256 and 2 period (latency about 10ms).
I can use jack without problem (no XRUN).

But if I stop jackd, I couldn't restart it without gettings tons of XRUN and then jackd stop.
It is the same things if I try to restart it as root (it seems it's not a realtime problem).
The only way to make it work is to use huge buffer (mini 4096), or switch to oss.
I have also disabled dmix on alsa, without success.
If someone has an idea on how to fix this problem...