Hey folks, this is an attempt to improve/refactor the dated panic notifiers infrastructure. This is strongly based in a suggestion made by Pter Mladek [0] some time ago, and it's finally ready. Below I'll detail the patch ordering, testing made, etc. First, a bit about the reason behind this. The panic notifiers list is an infrastructure that allows callbacks to execute during panic time. Happens that anybody can add functions there, no ordering is enforced (by default) and the decision to execute or not such notifiers before kdump may lead to high risk of failure in crash scenarios - default is not to execute any of them. There is a parameter acting as a switch for that. But some architectures require some notifiers, so..it's messy. The suggestion from Petr came after a patch submission to add a notifiers filter, allowing the notifiers selection by function name, which was welcomed by some people, but not by Petr, which claimed the code should indeed have a refactor - and it made a lot of sense, his suggestion makes code more clear and reliable. So, this series might be split in 3 portions: Part 1: the first 18 patches are mostly fixes (one or two might be considered improvements), mostly replacing spinlocks/mutexes with safer alternatives for atomic contexts, like spin_trylock, etc. We also focused on commenting everything that is possible and clean-up code. Part 2, the core: patches 19-25 are the main refactor, which splits the panic notifiers list in three, introduce the concept of panic notifier level and clean-up and highly comment the code, effectively leading to a more reliable and clear, yet highly customizable panic path. Part 3: The remaining 5 patches are fixes that _require the main refactor_ patches, they don't make sense without the core changes - but again, these are small fixes and not part of the main goal of refactoring the panic code. I've tried my best to make the patches the more "bisectable" as possible, so they tend to be self-contained and easy to backport (specially patches from part 1). Notice that the series is *based on 5.18-rc4* - usually a refactor like this would be based on linux-next, but since we have many fixes in the series, I kept it based on mainline tree. Of course I could change that in a subsequent iteration, if desired. Since this touches multiple architectures and drivers, it's very difficult to test it really (by executing all touched code). So, my tests split in two approaches: build tests and real tests, that involves panic triggering with and without kdump, changing panic notifiers level, etc. Build tests (using cross-compilers): alpha, arm, arm64, mips (sgi 22 and 32), parisc, s390, sparc, um, x86_64 (couldn't get a functional xtensa cross compiler). Real/full tests: x86_64 (Hyper-V and QEMU guests) + PowerPC (pseries guest). Here is the link with the .config files used: https://people.igalia.com/gpiccoli/panic_notifiers_configs/ (tried my best to build all the affected code). Finally, a bit about my CCing strategy: I've included everybody present in the original thread [0] plus some maintainers and other interested parties as CC in the full series. But the patches have individual CC lists, for people that are definitely related to them but might not care much for the whole series; nevertheless, _everybody_ mentioned at least once in some patch is CCed in this cover-letter. Hopefully I didn't forget to include anybody - all the mailing lists were CCed in the whole series. Apologies in advance if (a) you received emails you didn't want to or, (b) I forgot to include you but it was something considered interesting by you. Thanks in advance for reviews / comments / suggestions! Cheers, Guilherme [0] https://lore.kernel.org/lkml/YfPxvzSzDLjO5ldp@alley/ Guilherme G. Piccoli (30): x86/crash,reboot: Avoid re-disabling VMX in all CPUs on crash/restart ARM: kexec: Disable IRQs/FIQs also on crash CPUs shutdown path notifier: Add panic notifiers info and purge trailing whitespaces firmware: google: Convert regular spinlock into trylock on panic path misc/pvpanic: Convert regular spinlock into trylock on panic path soc: bcm: brcmstb: Document panic notifier action and remove useless header mips: ip22: Reword PANICED to PANICKED and remove useless header powerpc/setup: Refactor/untangle panic notifiers coresight: cpu-debug: Replace mutex with mutex_trylock on panic notifier alpha: Clean-up the panic notifier code um: Improve panic notifiers consistency and ordering parisc: Replace regular spinlock with spin_trylock on panic path s390/consoles: Improve panic notifiers reliability panic: Properly identify the panic event to the notifiers' callbacks bus: brcmstb_gisb: Clean-up panic/die notifiers drivers/hv/vmbus, video/hyperv_fb: Untangle and refactor Hyper-V panic notifiers tracing: Improve panic/die notifiers notifier: Show function names on notifier routines if DEBUG_NOTIFIERS is set panic: Add the panic hypervisor notifier list panic: Add the panic informational notifier list panic: Introduce the panic pre-reboot notifier list panic: Introduce the panic post-reboot notifier list printk: kmsg_dump: Introduce helper to inform number of dumpers panic: Refactor the panic path panic, printk: Add console flush parameter and convert panic_print to a notifier Drivers: hv: Do not force all panic notifiers to execute before kdump powerpc: Do not force all panic notifiers to execute before kdump panic: Unexport crash_kexec_post_notifiers powerpc: ps3, pseries: Avoid duplicate call to kmsg_dump() on panic um: Avoid duplicate call to kmsg_dump() .../admin-guide/kernel-parameters.txt | 54 ++- Documentation/admin-guide/sysctl/kernel.rst | 5 +- arch/alpha/kernel/setup.c | 40 +-- arch/arm/kernel/machine_kexec.c | 3 + arch/arm64/kernel/setup.c | 2 +- arch/mips/kernel/relocate.c | 2 +- arch/mips/sgi-ip22/ip22-reset.c | 13 +- arch/mips/sgi-ip32/ip32-reset.c | 3 +- arch/parisc/include/asm/pdc.h | 1 + arch/parisc/kernel/firmware.c | 27 +- arch/parisc/kernel/pdc_chassis.c | 3 +- arch/powerpc/include/asm/bug.h | 2 +- arch/powerpc/kernel/fadump.c | 8 - arch/powerpc/kernel/setup-common.c | 76 ++-- arch/powerpc/kernel/traps.c | 6 +- arch/powerpc/platforms/powernv/opal.c | 2 +- arch/powerpc/platforms/ps3/setup.c | 2 +- arch/powerpc/platforms/pseries/setup.c | 2 +- arch/s390/kernel/ipl.c | 4 +- arch/s390/kernel/setup.c | 19 +- arch/sparc/kernel/setup_32.c | 27 +- arch/sparc/kernel/setup_64.c | 29 +- arch/sparc/kernel/sstate.c | 3 +- arch/um/drivers/mconsole_kern.c | 10 +- arch/um/kernel/um_arch.c | 11 +- arch/x86/include/asm/cpu.h | 1 + arch/x86/kernel/crash.c | 8 +- arch/x86/kernel/reboot.c | 14 +- arch/x86/kernel/setup.c | 2 +- arch/x86/xen/enlighten.c | 2 +- arch/xtensa/platforms/iss/setup.c | 4 +- drivers/bus/brcmstb_gisb.c | 28 +- drivers/char/ipmi/ipmi_msghandler.c | 12 +- drivers/edac/altera_edac.c | 3 +- drivers/firmware/google/gsmi.c | 10 +- drivers/hv/hv_common.c | 12 - drivers/hv/vmbus_drv.c | 113 +++--- .../hwtracing/coresight/coresight-cpu-debug.c | 11 +- drivers/leds/trigger/ledtrig-activity.c | 4 +- drivers/leds/trigger/ledtrig-heartbeat.c | 4 +- drivers/leds/trigger/ledtrig-panic.c | 3 +- drivers/misc/bcm-vk/bcm_vk_dev.c | 6 +- drivers/misc/ibmasm/heartbeat.c | 16 +- drivers/misc/pvpanic/pvpanic.c | 14 +- drivers/net/ipa/ipa_smp2p.c | 5 +- drivers/parisc/power.c | 21 +- drivers/power/reset/ltc2952-poweroff.c | 4 +- drivers/remoteproc/remoteproc_core.c | 6 +- drivers/s390/char/con3215.c | 38 +- drivers/s390/char/con3270.c | 36 +- drivers/s390/char/raw3270.c | 18 + drivers/s390/char/raw3270.h | 1 + drivers/s390/char/sclp_con.c | 30 +- drivers/s390/char/sclp_vt220.c | 44 +-- drivers/s390/char/zcore.c | 5 +- drivers/soc/bcm/brcmstb/pm/pm-arm.c | 18 +- drivers/soc/tegra/ari-tegra186.c | 3 +- drivers/staging/olpc_dcon/olpc_dcon.c | 6 +- drivers/video/fbdev/hyperv_fb.c | 12 +- include/linux/console.h | 2 + include/linux/kmsg_dump.h | 7 + include/linux/notifier.h | 8 +- include/linux/panic.h | 3 - include/linux/panic_notifier.h | 12 +- include/linux/printk.h | 1 + kernel/hung_task.c | 3 +- kernel/kexec_core.c | 8 +- kernel/notifier.c | 48 ++- kernel/panic.c | 335 +++++++++++------- kernel/printk/printk.c | 76 ++++ kernel/rcu/tree.c | 1 - kernel/rcu/tree_stall.h | 3 +- kernel/trace/trace.c | 59 +-- .../selftests/pstore/pstore_crash_test | 5 +- 74 files changed, 953 insertions(+), 486 deletions(-) -- 2.36.0
