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    SubjectRe: [PATCH 3.18-rc3 v9 5/5] arm: smp: Handle ipi_cpu_backtrace() using FIQ (if available)
    Date
    Hi Daniel

    Am Dienstag, 25. November 2014, 17:26:41 schrieb Daniel Thompson:
    > Previous changes have introduced both a replacement default FIQ handler
    > and an implementation of arch_trigger_all_cpu_backtrace for ARM but
    > these are currently independent of each other.
    >
    > This patch plumbs together these features making it possible, on platforms
    > that support it, to trigger backtrace using FIQ.
    Does this ipi handler interfere in any way with set_fiq_handler?

    As far as i know there is only one FIQ handler vector so i guess there is a
    potential conflict. But i have not worked with IPI's so i might be completley
    wrong.

    Regards
    Tim

    > Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
    > ---
    > arch/arm/include/asm/smp.h | 3 +++
    > arch/arm/kernel/smp.c | 4 +++-
    > arch/arm/kernel/traps.c | 3 +++
    > 3 files changed, 9 insertions(+), 1 deletion(-)
    >
    > diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
    > index 18f5a554134f..b076584ac0fa 100644
    > --- a/arch/arm/include/asm/smp.h
    > +++ b/arch/arm/include/asm/smp.h
    > @@ -18,6 +18,8 @@
    > # error "<asm/smp.h> included in non-SMP build"
    > #endif
    >
    > +#define SMP_IPI_FIQ_MASK 0x0100
    > +
    > #define raw_smp_processor_id() (current_thread_info()->cpu)
    >
    > struct seq_file;
    > @@ -79,6 +81,7 @@ extern void arch_send_call_function_single_ipi(int cpu);
    > extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
    > extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask);
    >
    > +extern void ipi_cpu_backtrace(struct pt_regs *regs);
    > extern int register_ipi_completion(struct completion *completion, int cpu);
    >
    > struct smp_operations {
    > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
    > index 14c594a12bef..e923843562d9 100644
    > --- a/arch/arm/kernel/smp.c
    > +++ b/arch/arm/kernel/smp.c
    > @@ -539,7 +539,7 @@ static void ipi_cpu_stop(unsigned int cpu)
    > cpu_relax();
    > }
    >
    > -static void ipi_cpu_backtrace(struct pt_regs *regs)
    > +void ipi_cpu_backtrace(struct pt_regs *regs)
    > {
    > int cpu = smp_processor_id();
    >
    > @@ -580,6 +580,8 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
    > unsigned int cpu = smp_processor_id();
    > struct pt_regs *old_regs = set_irq_regs(regs);
    >
    > + BUILD_BUG_ON(SMP_IPI_FIQ_MASK != BIT(IPI_CPU_BACKTRACE));
    > +
    > if ((unsigned)ipinr < NR_IPI) {
    > trace_ipi_entry(ipi_types[ipinr]);
    > __inc_irq_stat(cpu, ipi_irqs[ipinr]);
    > diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
    > index 4dc45b38e56e..9eb05be9526e 100644
    > --- a/arch/arm/kernel/traps.c
    > +++ b/arch/arm/kernel/traps.c
    > @@ -483,6 +483,9 @@ asmlinkage void __exception_irq_entry
    > handle_fiq_as_nmi(struct pt_regs *regs) #ifdef CONFIG_ARM_GIC
    > gic_handle_fiq_ipi();
    > #endif
    > +#ifdef CONFIG_SMP
    > + ipi_cpu_backtrace(regs);
    > +#endif
    >
    > nmi_exit();



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