Red Hat Bugzilla – Bug 212273
FC6 does not support hyperthreading technology.
Last modified: 2015-01-04 17:29:14 EST
Description of problem:
I have a P4 3.0 GHZ with hyperthreading technology.I have to disable
hyperthreading in bios to get the computer to boot without hanging.It always
hangs when starting sshd,or sendmail.this also occurs with FC5.
Version-Release number of selected component (if applicable):
How reproducible:This occurs 100% of the time with hyperthreading enabled.
Steps to Reproduce:
1.turn on hyperthreading in bios.
2.turn computer on.
Actual results:It boots the kernel.When starting the services it hangs on
Expected results:This computer works fine using mandriva any version.Ubuntu and
Mepis using the SMP kernel to support the 2 virtual cores of the CPU also works
any chance you could hook this up to a serial console? or netconsole? maybe if
we get some kernel messages out of the thing just before the lockup we'll get
does booting with acpi=off make it work again ?
something else that might be worth a try.. boot up with ht disabled, and do a
chkconfig irqbalance off, and then reboot with it enabled. See if that makes it
I have a similar problem on a Dell Poweredge 400sc.
There is no setting to turn hyperthreading off in the bios.
I have no problems booting up, but hyperthreading is not used.
I see in dmesg:
CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 00004400
CPU: After vendor identify, caps: bfebfbff 00000000 00000000 00000000 00004400
CPU: Trace cache: 12K uops, L1 D cache: 8K
CPU: L2 cache: 128K
CPU: Hyper-Threading is disabled
CPU: After all inits, caps: bfebf3ff 00000000 00000000 00000080 00004400
Intel machine check architecture supported.
Intel machine check reporting enabled on CPU#0.
CPU0: Intel P4/Xeon Extended MCE MSRs (12) available
CPU0: Thermal monitoring enabled
Checking 'hlt' instruction... OK.
SMP alternatives: switching to UP code
Freeing SMP alternatives: 12k freed
ACPI: Core revision 20060707
CPU0: Intel(R) Celeron(R) CPU 2.00GHz stepping 09
Total of 1 processors activated (3994.07 BogoMIPS).
ENABLING IO-APIC IRQs
..TIMER: vector=0x31 apic1=0 pin1=2 apic2=-1 pin2=-1
Brought up 1 CPUs
cat /proc/cpuinfo gives me this:
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Celeron(R) CPU 2.00GHz
stepping : 9
cpu MHz : 1995.042
cache size : 128 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat
pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up cid xtpr
bogomips : 3994.07
Oops. Wrong bug number. Please ignore.
I have a very similar problem with my Amilo D 1840 laptop (P4 3.0GHz)
After installing FC6, the computer was impossible to boot, it always hang
somewhere in the start-up of services. It was not until I found a hint that one
should use the kernel option nolapic that I got it to work-according to some
postings I have read this is supposed to turn off HT? (I can conclude there is
no hyperthreading going on /proc/cpuinfo shows only one proc, and in messages I
have: "SMP alternatives: switching to UP code")
I can also confirm that the smp kernel hasn't worked either for FC3, FC4 or FC5,
hang in start-up (but the non-smp has of course been fine)
If I can provide you with some information for debugging this, please let me know.
I have identical symptoms but seem to have resolved the issue with my machine
(MSI 651 M-L board with an Intel 3.06 GHz HT-capable CPU, running the standard
FC6 installed kernel).
As mentioned above, on boot up with HyperThreading (HT) enabled, my system would
stall during the starting of services. Switching off HT in BIOS would enable a
successful boot up (using exactly the same kernel and boot-up parameters).
I tried deactivating a few non-essential (for me) services, including sendmail,
and went back into BIOS and enabled HT but on re-boot there was no change to the
situation - the stalls still persisted, always occurring during the loading of
Next, I tried passing "acpi=off" as boot parameter (as suggested in an earlier
post, above), I was able to successfully boot up and login - but without HT
activated, which should not be any surprise as HT needs ACPI (by using ACPI
tables for virtual processor discovery). [Reference: ACPI-HOWTO]
Using "acpi=ht" did not resolve the situation, with the system again stalled
during boot-up as before.
So I looked for something else to deactivate, whilst keeping ACPI active.
Elsewhere I read about deactivating APIC, so I removed the "apci=off" parameter
and instead passed "noapic" and the system booted-up all OK and with HT
activated - confirmed with 2 processors in /proc/cpuinfo
Hope this provides a useful lead/solution to others.
Fedora apologizes that these issues have not been resolved yet. We're
sorry it's taken so long for your bug to be properly triaged and acted
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these issues to this point.
The process we are following is outlined here:
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This bug is open for a Fedora version that is no longer maintained and
will not be fixed by Fedora. Therefore we are closing this bug.
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