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Date:	Wed, 29 Jun 2016 12:51:49 +0800
From:	Wei Jiangang <>
To:	<>
CC:	<>, <>, <>,
	<>, <>,
	Wei Jiangang <>
Subject: [PATCH 1/2] x86/apic: shutdown local APIC before I/O APIC during crash

commit <522e66464467> disables I/O APIC before shutdown of
the local APIC for both reboot and crash path.
and commit <2885432aaf15> declares that 'it still makes sense to
quiet IO APIC before disabling Local APIC'.

However, the former introduced a bug for crashdown.
If specify 'notsc' for capture-kernel, and then trigger crashdown.
The capture-kernel will be blocked at calibrate_delay_converge().

/* wait for "start of" clock tick */
ticks = jiffies;
while (ticks == jiffies)
    ; /* nothing */

serial console log as following,
[    0.000000] Linux version 4.7.0-rc2+ (root@...alhost.localdomain)
(gcc version 4.8.2 20140120 (Red Hat 4.8.2-16) (GCC) ) #2 SMP Wed Jun
[    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-4.7.0-rc2+
root=/dev/mapper/centos-root ro
vconsole.font=latarcyrheb-sun16 crashkernel=256M
vconsole.keymap=us console=tty0 console=ttyS0,115200n8 LANG=en_US.UTF-8
irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off
panic=10 rootflags=nofail acpi_no_memhotplug notsc
[    0.000000] tsc: Kernel compiled with CONFIG_X86_TSC, cannot disable
TSC completely
[    0.000000] clocksource: hpet: mask: 0xffffffff max_cycles:
0xffffffff, max_idle_ns: 133484882848 ns
[    0.000000] tsc: Fast TSC calibration using PIT
[    0.000000] tsc: Detected 3192.714 MHz processor
[    0.000000] Calibrating delay loop...

The bug remains and unsolved for a long time, since 2013.
I find the arch-criminal by bisect.

The commit <522e66464467> used to fix erratum AVR31 for "Intel Atom
Processor C2000 Product Family Specification Update".
You can find the doc at

It doesn't make sense that change the order of disabling between
I/O APIC and local APIC just for a certain model C2000.
And I couldn't find any related descriptions for Intel 64 and IA-32 Arch.

so, I want to revert the crash part of commit <522e66464467>.

Signed-off-by: Wei Jiangang <>
 arch/x86/kernel/crash.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9ef978d69c22..9aa0235c1f7d 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -179,12 +179,13 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
+	lapic_shutdown();
 #ifdef CONFIG_X86_IO_APIC
 	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
-	lapic_shutdown();

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