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| author | Fenghua Yu <fenghua.yu@intel.com> | 2013-12-05 01:07:49 +0100 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2013-12-05 04:33:21 +0100 |
| commit | 2885432aaf15c1b7e65c787bfe7c5fec428296f0 (patch) | |
| tree | 4b2157a32cbd86ec75f82ff1311eb66bea44bf6b /arch/x86/kernel/reboot.c | |
| parent | x86, bitops: Correct the assembly constraints to testing bitops (diff) | |
| download | linux-2885432aaf15c1b7e65c787bfe7c5fec428296f0.tar.xz linux-2885432aaf15c1b7e65c787bfe7c5fec428296f0.zip | |
x86/apic, doc: Justification for disabling IO APIC before Local APIC
Since erratum AVR31 in "Intel Atom Processor C2000 Product Family
Specification Update" is now published, I added a justification
comment for disabling IO APIC before Local APIC, as changed in commit:
522e66464467 x86/apic: Disable I/O APIC before shutdown of the local APIC
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1386202069-51515-1-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/reboot.c')
| -rw-r--r-- | arch/x86/kernel/reboot.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index da3c599584a3..c752cb43e52f 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -558,6 +558,17 @@ void native_machine_shutdown(void) { /* Stop the cpus and apics */ #ifdef CONFIG_X86_IO_APIC + /* + * Disabling IO APIC before local APIC is a workaround for + * erratum AVR31 in "Intel Atom Processor C2000 Product Family + * Specification Update". In this situation, interrupts that target + * a Logical Processor whose Local APIC is either in the process of + * being hardware disabled or software disabled are neither delivered + * nor discarded. When this erratum occurs, the processor may hang. + * + * Even without the erratum, it still makes sense to quiet IO APIC + * before disabling Local APIC. + */ disable_IO_APIC(); #endif |