From 5cc05910f26e6fd6da15f052f86f6150e4b91664 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 2 May 2018 23:07:28 +1000 Subject: [PATCH] powerpc/64s: Wire up arch_trigger_cpumask_backtrace() This allows eg. the RCU stall detector, or the soft/hardlockup detectors to trigger a backtrace on all CPUs. We implement this by sending a "safe" NMI, which will actually only send an IPI. Unfortunately the generic code prints "NMI", so that's a little confusing but we can probably live with it. If one of the CPUs doesn't respond to the IPI, we then print some info from it's paca and do a backtrace based on its saved_r1. Example output: INFO: rcu_sched detected stalls on CPUs/tasks: 2-...0: (0 ticks this GP) idle=1be/1/4611686018427387904 softirq=1055/1055 fqs=25735 (detected by 4, t=58847 jiffies, g=58, c=57, q=1258) Sending NMI from CPU 4 to CPUs 2: CPU 2 didn't respond to backtrace IPI, inspecting paca. irq_soft_mask: 0x01 in_mce: 0 in_nmi: 0 current: 3623 (bash) Back trace of paca->saved_r1 (0xc0000000e1c83ba0) (possibly stale): Call Trace: [c0000000e1c83ba0] [0000000000000014] 0x14 (unreliable) [c0000000e1c83bc0] [c000000000765798] lkdtm_do_action+0x48/0x80 [c0000000e1c83bf0] [c000000000765a40] direct_entry+0x110/0x1b0 [c0000000e1c83c90] [c00000000058e650] full_proxy_write+0x90/0xe0 [c0000000e1c83ce0] [c0000000003aae3c] __vfs_write+0x6c/0x1f0 [c0000000e1c83d80] [c0000000003ab214] vfs_write+0xd4/0x240 [c0000000e1c83dd0] [c0000000003ab5cc] ksys_write+0x6c/0x110 [c0000000e1c83e30] [c00000000000b860] system_call+0x58/0x6c Signed-off-by: Michael Ellerman Reviewed-by: Nicholas Piggin --- arch/powerpc/include/asm/nmi.h | 6 +++++ arch/powerpc/kernel/stacktrace.c | 51 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h index 9c80939..0f571e0 100644 --- a/arch/powerpc/include/asm/nmi.h +++ b/arch/powerpc/include/asm/nmi.h @@ -8,4 +8,10 @@ extern void arch_touch_nmi_watchdog(void); static inline void arch_touch_nmi_watchdog(void) {} #endif +#if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_STACKTRACE) +extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask, + bool exclude_self); +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace +#endif + #endif /* _ASM_NMI_H */ diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index 8dd6ba0..b4f134e 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -22,6 +23,8 @@ #include #include +#include + /* * Save stack-backtrace addresses into a stack_trace buffer. */ @@ -194,3 +197,51 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, } EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable); #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ + +#ifdef CONFIG_PPC_BOOK3S_64 +static void handle_backtrace_ipi(struct pt_regs *regs) +{ + nmi_cpu_backtrace(regs); +} + +static void raise_backtrace_ipi(cpumask_t *mask) +{ + unsigned int cpu; + + for_each_cpu(cpu, mask) { + if (cpu == smp_processor_id()) + handle_backtrace_ipi(NULL); + else + smp_send_safe_nmi_ipi(cpu, handle_backtrace_ipi, 5 * USEC_PER_SEC); + } + + for_each_cpu(cpu, mask) { + struct paca_struct *p = paca_ptrs[cpu]; + + cpumask_clear_cpu(cpu, mask); + + pr_warn("CPU %d didn't respond to backtrace IPI, inspecting paca.\n", cpu); + if (!virt_addr_valid(p)) { + pr_warn("paca pointer appears corrupt? (%px)\n", p); + continue; + } + + pr_warn("irq_soft_mask: 0x%02x in_mce: %d in_nmi: %d", + p->irq_soft_mask, p->in_mce, p->in_nmi); + + if (virt_addr_valid(p->__current)) + pr_cont(" current: %d (%s)\n", p->__current->pid, + p->__current->comm); + else + pr_cont(" current pointer corrupt? (%px)\n", p->__current); + + pr_warn("Back trace of paca->saved_r1 (0x%016llx) (possibly stale):\n", p->saved_r1); + show_stack(p->__current, (unsigned long *)p->saved_r1); + } +} + +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) +{ + nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); +} +#endif /* CONFIG_PPC64 */ -- 2.7.4