This is an attempt to resurrect Sumit's old patch series [1] that allowed us to use the arm64 pseudo-NMI to get backtraces of CPUs and also to round up CPUs in kdb/kgdb. The last post from Sumit that I could find was v7, so I called this series v8. I haven't copied all of his old changelongs here, but you can find them from the link. Since v7, I have: * Addressed the small amount of feedback that was there for v7. * Rebased. * Added a new patch that prevents us from spamming the logs with idle tasks. * Added an extra patch to gracefully fall back to regular IPIs if pseudo-NMIs aren't there. Since there appear to be a few different patches series related to being able to use NMIs to get stack traces of crashed systems, let me try to organize them to the best of my understanding: a) This series. On its own, a) will (among other things) enable stack traces of all running processes with the soft lockup detector if you've enabled the sysctl "kernel.softlockup_all_cpu_backtrace". On its own, a) doesn't give a hard lockup detector. b) A different recently-posted series [2] that adds a hard lockup detector based on perf. On its own, b) gives a stack crawl of the locked up CPU but no stack crawls of other CPUs (even if they're locked too). Together with a) + b) we get everything (full lockup detect, full ability to get stack crawls). c) The old Android "buddy" hard lockup detector [3] that I'm considering trying to upstream. If b) lands then I believe c) would be redundant (at least for arm64). c) on its own is really only useful on arm64 for platforms that can print CPU_DBGPCSR somehow (see [4]). a) + c) is roughly as good as a) + b). [1] https://lore.kernel.org/linux-arm-kernel/1604317487-14543-1-git-send-email-sumit.garg@xxxxxxxxxx/ [2] https://lore.kernel.org/linux-arm-kernel/20220903093415.15850-1-lecopzer.chen@xxxxxxxxxxxx/ [3] https://issuetracker.google.com/172213097 [4] https://issuetracker.google.com/172213129 Changes in v8: - dynamic_ipi_setup() and dynamic_ipi_teardown() no longer take cpu param - dynamic_ipi_setup() and dynamic_ipi_teardown() no longer take cpu param - Add loongarch support, too - Removed "#ifdef CONFIG_SMP" since arm64 is always SMP - "Tag the arm64 idle functions as __cpuidle" new for v8 - "Provide a stub kgdb_nmicallback() if !CONFIG_KGDB" new for v8 - "Fallback to a regular IPI if NMI isn't enabled" new for v8 Douglas Anderson (3): arm64: idle: Tag the arm64 idle functions as __cpuidle kgdb: Provide a stub kgdb_nmicallback() if !CONFIG_KGDB arm64: ipi_nmi: Fallback to a regular IPI if NMI isn't enabled Sumit Garg (7): arm64: Add framework to turn IPI as NMI irqchip/gic-v3: Enable support for SGIs to act as NMIs arm64: smp: Assign and setup an IPI as NMI nmi: backtrace: Allow runtime arch specific override arm64: ipi_nmi: Add support for NMI backtrace kgdb: Expose default CPUs roundup fallback mechanism arm64: kgdb: Roundup cpus using IPI as NMI arch/arm/include/asm/irq.h | 2 +- arch/arm/kernel/smp.c | 3 +- arch/arm64/include/asm/irq.h | 4 ++ arch/arm64/include/asm/nmi.h | 17 +++++ arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/idle.c | 4 +- arch/arm64/kernel/ipi_nmi.c | 103 +++++++++++++++++++++++++++++++ arch/arm64/kernel/kgdb.c | 18 ++++++ arch/arm64/kernel/smp.c | 8 +++ arch/loongarch/include/asm/irq.h | 2 +- arch/loongarch/kernel/process.c | 3 +- arch/mips/include/asm/irq.h | 2 +- arch/mips/kernel/process.c | 3 +- arch/powerpc/include/asm/nmi.h | 2 +- arch/powerpc/kernel/stacktrace.c | 3 +- arch/sparc/include/asm/irq_64.h | 2 +- arch/sparc/kernel/process_64.c | 4 +- arch/x86/include/asm/irq.h | 2 +- arch/x86/kernel/apic/hw_nmi.c | 3 +- drivers/irqchip/irq-gic-v3.c | 29 ++++++--- include/linux/kgdb.h | 13 ++++ include/linux/nmi.h | 12 ++-- kernel/debug/debug_core.c | 8 ++- 23 files changed, 217 insertions(+), 32 deletions(-) create mode 100644 arch/arm64/include/asm/nmi.h create mode 100644 arch/arm64/kernel/ipi_nmi.c -- 2.40.0.634.g4ca3ef3211-goog
