Commit-ID: 2885432aaf15c1b7e65c787bfe7c5fec428296f0 Gitweb: http://git.kernel.org/tip/2885432aaf15c1b7e65c787bfe7c5fec428296f0 Author: Fenghua Yu <fenghua...@intel.com> AuthorDate: Wed, 4 Dec 2013 16:07:49 -0800 Committer: H. Peter Anvin <h...@linux.intel.com> CommitDate: Wed, 4 Dec 2013 19:33:21 -0800
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...@intel.com> Link: http://lkml.kernel.org/r/1386202069-51515-1-git-send-email-fenghua...@intel.com Signed-off-by: H. Peter Anvin <h...@linux.intel.com> --- arch/x86/kernel/reboot.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index da3c599..c752cb4 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
