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SubjectRe: [V3 PATCH 0/4] Fix race issues among panic, NMI and crash_kexec
JFYI I have those patches tested on the largish box. Will come back to
you as soon as I have some feedback.

I will also try to review these patches sometimes next week.

Thanks!

On Thu 06-08-15 14:45:43, Hidehiro Kawai wrote:
> When an HA cluster software or administrator detects non-response
> of a host, they issue an NMI to the host to completely stop current
> works and take a crash dump. If the kernel has already panicked
> or is capturing a crash dump at that time, further NMI can cause
> a crash dump failure.
>
> Also, crash_kexec() called from oops context and panic() can
> cause race conditions.
>
> To solve these issue, this patch set does following things:
>
> - Don't panic on NMI if the kernel has already panicked
> - Extend exclusion control currently done by panic_lock to crash_kexec
> - Introduce "noextnmi" boot option which masks external NMI at the
> boot time (supported only for x86)
>
> V3:
> - Introduce nmi_panic() macro to reduce code duplication
> - In the case of panic on NMI, don't return from NMI handlers
> if another cpu already panicked
>
> V2:
> - Use atomic_cmpxchg() instead of current spin_trylock() to exclude
> concurrent accesses to panic() and crash_kexec()
> - Don't introduce no-lock version of panic() and crash_kexec()
>
> ---
>
> Hidehiro Kawai (4):
> panic/x86: Fix re-entrance problem due to panic on NMI
> panic/x86: Allow cpus to save registers even if they are looping in NMI context
> kexec: Fix race between panic() and crash_kexec() called directly
> x86/apic: Introduce noextnmi boot option
>
>
> Documentation/kernel-parameters.txt | 4 ++++
> arch/x86/kernel/apic/apic.c | 17 ++++++++++++++++-
> arch/x86/kernel/nmi.c | 15 +++++++++++----
> arch/x86/kernel/reboot.c | 11 +++++++++++
> include/linux/kernel.h | 21 +++++++++++++++++++++
> kernel/kexec.c | 20 ++++++++++++++++++++
> kernel/panic.c | 23 ++++++++++++++++++++---
> kernel/watchdog.c | 5 +++--
> 8 files changed, 106 insertions(+), 10 deletions(-)
>
>
> --
> Hidehiro Kawai
> Hitachi, Ltd. Research & Development Group
>
>

--
Michal Hocko
SUSE Labs


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