When an HA clustering software or administrator detects unresponsiveness 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 "apic_extnmi=none" boot option which masks external NMI NMI at the boot time Additionally, "apic_extnmi=all" is provieded. This option unmasks external NMI for all CPUs. This would help cause kernel panic even if CPU 0 can't handle an external NMI due to hang-up in NMI context or being handled by other NMI handlers. This patch set can be applied to current -tip tree. V6: - Update comments and patch descriptions all over the patch series - Add documentation for kernel.panic_on_io_nmi sysctl (PATCH 6/6) - Separate PATCH 5/6 from PATCH 2/6 because the portion is actually needed for "apic_extnmi=all" case introduced by PATCH 4/6 - ...and various fixes (please see the change logs in each patch description for details) V5: https://lkml.org/lkml/2015/11/20/228 - Use WRITE_ONCE() for crash_ipi_done to keep the instruction order (PATCH 2/4) - Address concurrent unknown/external NMI case, too (PATCH 2/4) - Fix build errors (PATCH 3/4) - Rename "noextnmi" boot option to "apic_extnmi" and expand its feature (PATCH 4/4) V4: https://lkml.org/lkml/2015/9/25/193 - 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 (6): 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 apic_extnmi boot option x86/nmi: Fix to save registers for crash dump on external NMI broadcast Documentation: Add documentation for kernel.panic_on_io_nmi sysctl Documentation/kernel-parameters.txt | 9 +++++++++ Documentation/sysctl/kernel.txt | 15 +++++++++++++++ arch/x86/include/asm/apic.h | 5 +++++ arch/x86/include/asm/reboot.h | 1 + arch/x86/kernel/apic/apic.c | 35 +++++++++++++++++++++++++++++++++-- arch/x86/kernel/nmi.c | 27 ++++++++++++++++++++++----- arch/x86/kernel/reboot.c | 28 ++++++++++++++++++++++++++++ include/linux/kernel.h | 29 +++++++++++++++++++++++++++++ include/linux/kexec.h | 2 ++ kernel/kexec_core.c | 30 +++++++++++++++++++++++++++++- kernel/panic.c | 29 ++++++++++++++++++++++++----- kernel/watchdog.c | 2 +- 12 files changed, 198 insertions(+), 14 deletions(-) -- Hidehiro Kawai Hitachi, Ltd. Research & Development Group
