Re: [PATCH 3.19-rc2 v14 0/7] arm: Implement arch_trigger_all_cpu_backtrace

From: Daniel Thompson
Date: Tue Jan 20 2015 - 05:25:31 EST


On 13/01/15 10:26, Daniel Thompson wrote:
> Hi Thomas, Hi Jason:
> Patches 1 to 3 are for you (and should be separable from the rest
> of the series). The patches haven't changes since the last time
> I posted them. The changes in v14 tidy up the later part of the
> patch set in order to share more code between x86 and arm.

No review comments! Have I finally got this right?

If so it possible and/or sensible to get patches 1-3 in a tree that
feeds linux-next. I'd really like the gic changes to meet the various
ARM build and boot bots.


Daniel.



>
> This patchset modifies the GIC driver to allow it, on supported
> platforms, to route IPI interrupts to FIQ and uses this feature to
> implement arch_trigger_all_cpu_backtrace for arm.
>
> On platforms not capable of supporting FIQ the signal to generate a
> backtrace we fall back to using IRQ for propagation instead (relying on
> a timeout to avoid wedging the CPU requesting the backtrace if other
> CPUs are not responsive).
>
> It has been tested on two systems capable of supporting grouping
> (Freescale i.MX6 and STiH416) and two that do not (vexpress-a9 and
> Qualcomm Snapdragon 600).
>
> v14:
>
> * Moved a nmi_vprintk() and friends from arch/x86/kernel/apic/hw_nmi.c
> to printk.c (Steven Rostedt)
>
> v13:
>
> * Updated the code to print the backtrace to replicate Steven Rostedt's
> x86 work to make SysRq-l safe. This is pretty much a total rewrite of
> patches 4 and 5.
>
> v12:
>
> * Squash first two patches into a single one and re-describe
> (Thomas Gleixner).
>
> * Improve description of "irqchip: gic: Make gic_raise_softirq FIQ-safe"
> (Thomas Gleixner).
>
> v11:
>
> * Optimized gic_raise_softirq() by replacing a register read with
> a memory read (Jason Cooper).
>
> v10:
>
> * Add a further patch to optimize away some of the locking on systems
> where CONFIG_BL_SWITCHER is not set (Marc Zyngier). Compiles OK with
> exynos_defconfig (which is the only defconfig to set this option).
>
> * Whitespace fixes in patch 4. That patch previously used spaces for
> alignment of new constants but the rest of the file used tabs.
>
> v9:
>
> * Improved documentation and structure of initial patch (now initial
> two patches) to make gic_raise_softirq() safe to call from FIQ
> (Thomas Gleixner).
>
> * Avoid masking interrupts during gic_raise_softirq(). The use of the
> read lock makes this redundant (because we can safely re-enter the
> function).
>
> v8:
>
> * Fixed build on arm64 causes by a spurious include file in irq-gic.c.
>
> v7-2 (accidentally released twice with same number):
>
> * Fixed boot regression on vexpress-a9 (reported by Russell King).
>
> * Rebased on v3.18-rc3; removed one patch from set that is already
> included in mainline.
>
> * Dropped arm64/fiq.h patch from the set (still useful but not related
> to issuing backtraces).
>
> v7:
>
> * Re-arranged code within the patch series to fix a regression
> introduced midway through the series and corrected by a later patch
> (testing by Olof's autobuilder). Tested offending patch in isolation
> using defconfig identified by the autobuilder.
>
> v6:
>
> * Renamed svc_entry's call_trace argument to just trace (example code
> from Russell King).
>
> * Fixed mismatched ENDPROC() in __fiq_abt (example code from Russell
> King).
>
> * Modified usr_entry to optional avoid calling into the trace code and
> used this in FIQ entry from usr path. Modified corresponding exit code
> to avoid calling into trace code and the scheduler (example code from
> Russell King).
>
> * Ensured the default FIQ register state is restored when the default
> FIQ handler is reinstalled (example code from Russell King).
>
> * Renamed no_fiq_insn to dfl_fiq_insn to reflect the effect of adopting
> a default FIQ handler.
>
> * Re-instated fiq_safe_migration_lock and associated logic in
> gic_raise_softirq(). gic_raise_softirq() is called by wake_up_klogd()
> in the console unlock logic.
>
> v5:
>
> * Rebased on 3.17-rc4.
>
> * Removed a spurious line from the final "glue it together" patch
> that broke the build.
>
> v4:
>
> * Replaced push/pop with stmfd/ldmfd respectively (review of Nicolas
> Pitre).
>
> * Really fix bad pt_regs pointer generation in __fiq_abt.
>
> * Remove fiq_safe_migration_lock and associated logic in
> gic_raise_softirq() (review of Russell King)
>
> * Restructured to introduce the default FIQ handler first, before the
> new features (review of Russell King).
>
> v3:
>
> * Removed redundant header guards from arch/arm64/include/asm/fiq.h
> (review of Catalin Marinas).
>
> * Moved svc_exit_via_fiq macro to entry-header.S (review of Nicolas
> Pitre).
>
> v2:
>
> * Restructured to sit nicely on a similar FYI patchset from Russell
> King. It now effectively replaces the work in progress final patch
> with something much more complete.
>
> * Implemented (and tested) a Thumb-2 implementation of svc_exit_via_fiq
> (review of Nicolas Pitre)
>
> * Dropped the GIC group 0 workaround patch. The issue of FIQ interrupts
> being acknowledged by the IRQ handler does still exist but should be
> harmless because the IRQ handler will still wind up calling
> ipi_cpu_backtrace().
>
> * Removed any dependency on CONFIG_FIQ; all cpu backtrace effectively
> becomes a platform feature (although the use of non-maskable
> interrupts to implement it is best effort rather than guaranteed).
>
> * Better comments highlighting usage of RAZ/WI registers (and parts of
> registers) in the GIC code.
>
> Changes *before* v1:
>
> * This patchset is a hugely cut-down successor to "[PATCH v11 00/19]
> arm: KGDB NMI/FIQ support". Thanks to Thomas Gleixner for suggesting
> the new structure. For historic details see:
> https://lkml.org/lkml/2014/9/2/227
>
> * Fix bug in __fiq_abt (no longer passes a bad struct pt_regs value).
> In fixing this we also remove the useless indirection previously
> found in the fiq_handler macro.
>
> * Make default fiq handler "always on" by migrating from fiq.c to
> traps.c and replace do_unexp_fiq with the new handler (review
> of Russell King).
>
> * Add arm64 version of fiq.h (review of Russell King)
>
> * Removed conditional branching and code from irq-gic.c, this is
> replaced by much simpler code that relies on the GIC specification's
> heavy use of read-as-zero/write-ignored (review of Russell King)
>
>
> Daniel Thompson (7):
> irqchip: gic: Optimize locking in gic_raise_softirq
> irqchip: gic: Make gic_raise_softirq FIQ-safe
> irqchip: gic: Introduce plumbing for IPI FIQ
> printk: Simple implementation for NMI backtracing
> x86/nmi: Use common printk functions
> ARM: Add support for on-demand backtrace of other CPUs
> ARM: Fix on-demand backtrace triggered by IRQ
>
> arch/Kconfig | 3 +
> arch/arm/Kconfig | 1 +
> arch/arm/include/asm/hardirq.h | 2 +-
> arch/arm/include/asm/irq.h | 5 +
> arch/arm/include/asm/smp.h | 3 +
> arch/arm/kernel/smp.c | 84 +++++++++++++++++
> arch/arm/kernel/traps.c | 8 +-
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/apic/hw_nmi.c | 94 ++-----------------
> drivers/irqchip/irq-gic.c | 203 +++++++++++++++++++++++++++++++++++++---
> include/linux/irqchip/arm-gic.h | 8 ++
> include/linux/printk.h | 22 +++++
> kernel/printk/printk.c | 122 ++++++++++++++++++++++++
> 13 files changed, 452 insertions(+), 104 deletions(-)
>
> --
> 1.9.3
>

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