HyperThreading not working under 2.4.21

["R.C" <rafaled@wanadoo.fr>]

Hello there,

I recently tried to upgrade to the 2.4.21 vanilla kernel. I am using a Pentium 
IV 3,06ghz HT. Amongst other things, I enabled the following options: 
"Pentium-4 processor Family, SMP support, ACPI support". I tried it with both 
ACPI support on and off. I can join a copy of my .config if it is required.

Anyway, when booting the 2.4.21 kernel my second logical processor
is not detected at all. All works as if I had only one processor. There is no 
error message. A cat /proc/cpuinfo reports only one cpu.

This problem only occurs with 2.4.21 kernel. My HT processor was working 
perfectly with any branch of the 2.4.20 serie (I was using 2.4.20-ck6). My 
second logical processor was perfectly recognized. Thus, it does not seem to 
be a problem with bios or mb settings.

A "very" quick search through google made me conclude that this problem had 
not been reported yet so please, forgive me if you are all already aware of 
such a problem.

Best regards,

            R.C


P.S: join a copy to my e-mail adress if you may.