When an HA clustering software or administrator detects unresponsivenes 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 issues, this patch set does following things: - Don't call 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) This patch set can be applied to current -tip tree. V4: - Improve comments and descriptions (PATCH 1/4 to 3/4) - Use new __crash_kexec(), no exclusion check version of crash_kexec(), instead of checking if panic_cpu is the current cpu or not (PATCH 3/4) V3: https://lkml.org/lkml/2015/8/6/39 - 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: https://lkml.org/lkml/2015/7/27/31 - 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() V1: https://lkml.org/lkml/2015/7/22/81 --- 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 | 16 ++++++++++++---- arch/x86/kernel/reboot.c | 11 +++++++++++ include/linux/kernel.h | 21 +++++++++++++++++++++ include/linux/kexec.h | 1 + kernel/kexec_core.c | 26 +++++++++++++++++++++++++- kernel/panic.c | 29 ++++++++++++++++++++++++----- kernel/watchdog.c | 5 +++-- 9 files changed, 117 insertions(+), 13 deletions(-) -- Hidehiro Kawai Hitachi, Ltd. Research & Development Group
