cregit-Linux how code gets into the kernel

Release 4.9 lib/nmi_backtrace.c

Directory: lib
 *  NMI backtrace support
 * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
 * with the following header:
 *  HW NMI watchdog support
 *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
 *  Arch specific calls to support NMI watchdog
 *  Bits copied from original nmi.c file
#include <linux/cpumask.h>
#include <linux/delay.h>
#include <linux/kprobes.h>
#include <linux/nmi.h>
#include <linux/cpu.h>

#ifdef arch_trigger_cpumask_backtrace
/* For reliability, we're prepared to waste bits here. */
static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;

/* "in progress" flag of arch_trigger_cpumask_backtrace */

static unsigned long backtrace_flag;

 * When raise() is called it will be passed a pointer to the
 * backtrace_mask. Architectures that call nmi_cpu_backtrace()
 * directly from their raise() functions may rely on the mask
 * they are passed being updated as a side effect of this call.

void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self, void (*raise)(cpumask_t *mask)) { int i, this_cpu = get_cpu(); if (test_and_set_bit(0, &backtrace_flag)) { /* * If there is already a trigger_all_cpu_backtrace() in progress * (backtrace_flag == 1), don't output double cpu dump infos. */ put_cpu(); return; } cpumask_copy(to_cpumask(backtrace_mask), mask); if (exclude_self) cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); /* * Don't try to send an NMI to this cpu; it may work on some * architectures, but on others it may not, and we'll get * information at least as useful just by doing a dump_stack() here. * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit. */ if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask))) nmi_cpu_backtrace(NULL); if (!cpumask_empty(to_cpumask(backtrace_mask))) { pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n", this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask)); raise(to_cpumask(backtrace_mask)); } /* Wait for up to 10 seconds for all CPUs to do the backtrace */ for (i = 0; i < 10 * 1000; i++) { if (cpumask_empty(to_cpumask(backtrace_mask))) break; mdelay(1); touch_softlockup_watchdog(); } /* * Force flush any remote buffers that might be stuck in IRQ context * and therefore could not run their irq_work. */ printk_nmi_flush(); clear_bit_unlock(0, &backtrace_flag); put_cpu(); }


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bool nmi_cpu_backtrace(struct pt_regs *regs) { int cpu = smp_processor_id(); if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { if (regs && cpu_in_idle(instruction_pointer(regs))) { pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n", cpu, instruction_pointer(regs)); } else { pr_warn("NMI backtrace for cpu %d\n", cpu); if (regs) show_regs(regs); else dump_stack(); } cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); return true; } return false; }


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NOKPROBE_SYMBOL(nmi_cpu_backtrace); #endif

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Directory: lib