From: Michal Schmidt on
On my system with AMD Phenom II X6 I am seeing pauses at boot (usually during
udev startup) which require a key press to continue. It only happens if C1E is
enabled in the BIOS.

It's caused by the APIC timer's inability to wake up the CPU from C1E (AMD
erratum #400). Linux has a workaround for it, but it's not being applied
correctly in this case. Though c1e_idle() detects C1E just fine, by the time
acpi_idle ('processor.ko' module) takes over, it is forgotten.

After AMD C1E is detected, it is not sufficient to flag it in boot_cpu_data,
because the flag will get cleared in identify_cpu() when more CPUs are brought
up later. The fix is to mark the flag as forced.

The additional call to set_cpu_cap() is just to make sure the flag is set even
on the CPUs that are already up and /proc/cpuinfo shows 'amdc1e' on all.

Also fix indentation in the function.

Signed-off-by: Michal Schmidt <mschmidt(a)>

arch/x86/kernel/process.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index e7e3521..f3520a8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -589,7 +589,7 @@ static void c1e_idle(void)
if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
mark_tsc_unstable("TSC halt in AMD C1E");
printk(KERN_INFO "System has AMD C1E enabled\n");
- set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
+ setup_force_cpu_cap(X86_FEATURE_AMDC1E);

@@ -605,6 +605,7 @@ static void c1e_idle(void)
printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
+ set_cpu_cap(&current_cpu_data, X86_FEATURE_AMDC1E);
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

@@ -614,9 +615,9 @@ static void c1e_idle(void)
* The switch back from broadcast mode needs to be
* called with interrupts disabled.
- local_irq_disable();
- clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
- local_irq_enable();
+ local_irq_disable();
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+ local_irq_enable();
} else

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