Messages in this thread Patch in this message | | | Date | Wed, 28 May 2008 20:25:27 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [patch 06/11] x86: nmi_32/64.c - use apic_write_around instead of apic_write |
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[Maciej W. Rozycki - Wed, May 28, 2008 at 05:13:08PM +0100] | On Wed, 28 May 2008, Cyrill Gorcunov wrote: | | > Could you take a look please on | > | > http://lkml.org/lkml/2008/5/26/146 | > | > i'm investigateting what is happening (Adrian pointed on | > main reason I think) but can't understand why is that. | | Do you have a link with the patch included? | | Maciej |
Here is the patch itself:
--- x86: nmi_32.c - add nmi_watchdog_default helper
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com> ---
Index: linux-2.6.git/arch/x86/kernel/nmi_32.c ==================================================================== --- linux-2.6.git.orig/arch/x86/kernel/nmi_32.c 2008-05-24 13:01:21.000000000 +0400 +++ linux-2.6.git/arch/x86/kernel/nmi_32.c 2008-05-24 13:04:20.000000000 +0400 @@ -51,6 +51,17 @@ static DEFINE_PER_CPU(short, wd_enabled) static int endflag __initdata = 0; +/* Run after command line and cpu_init init, but before all other checks */ +void nmi_watchdog_default(void) +{ + if (nmi_watchdog != NMI_DEFAULT) + return; + if (lapic_watchdog_ok()) + nmi_watchdog = NMI_LOCAL_APIC; + else + nmi_watchdog = NMI_IO_APIC; +} + #ifdef CONFIG_SMP /* The performance counters used by NMI_LOCAL_APIC don't trigger when * the CPU is idle. To make sure the NMI watchdog really ticks on all @@ -437,12 +448,8 @@ int proc_nmi_enabled(struct ctl_table *t return -EIO; } - if (nmi_watchdog == NMI_DEFAULT) { - if (lapic_watchdog_ok()) - nmi_watchdog = NMI_LOCAL_APIC; - else - nmi_watchdog = NMI_IO_APIC; - } + /* if nmi_watchdog is not set yet, then set it */ + nmi_watchdog_default(); if (nmi_watchdog == NMI_LOCAL_APIC) { if (nmi_watchdog_enabled) Index: linux-2.6.git/include/asm-x86/nmi.h ==================================================================== --- linux-2.6.git.orig/include/asm-x86/nmi.h 2008-05-24 13:00:50.000000000 +0400 +++ linux-2.6.git/include/asm-x86/nmi.h 2008-05-24 13:04:51.000000000 +0400 @@ -38,11 +38,9 @@ static inline void unset_nmi_pm_callback #ifdef CONFIG_X86_64 extern void default_do_nmi(struct pt_regs *); -extern void nmi_watchdog_default(void); -#else -#define nmi_watchdog_default() do {} while (0) #endif +extern void nmi_watchdog_default(void); extern void die_nmi(char *str, struct pt_regs *regs, int do_panic); extern int check_nmi_watchdog(void); extern int nmi_watchdog_enabled; --- So I've moved a part of code (32bit) from proc_nmi_enabled() to nmi_watchdog_default() BUT this nmi_watchdog_default() also called from smpboot.c:native_smp_prepare_cpus() and before this patch this call was just an empty call (and eliminated by gcc I think) now it's not empy. But how it leads to hang I can't understand. The only thing is done - nmi_watchdog is set to NMI_LOCAL_APIC or NMI_IO_APIC and my only suspicious is that something happens asynchronously and leads to machine hang. Let me know if I wrote in obscure manner.
- Cyrill -
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