163 lines
4.2 KiB
C
163 lines
4.2 KiB
C
/*
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* NMI backtrace support
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*
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* Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
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* with the following header:
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*
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* HW NMI watchdog support
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*
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* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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*
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* Arch specific calls to support NMI watchdog
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*
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* Bits copied from original nmi.c file
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*/
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#include <linux/cpumask.h>
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#include <linux/delay.h>
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#include <linux/kprobes.h>
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#include <linux/nmi.h>
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#include <linux/seq_buf.h>
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#ifdef arch_trigger_all_cpu_backtrace
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/* For reliability, we're prepared to waste bits here. */
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static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
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static cpumask_t printtrace_mask;
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#define NMI_BUF_SIZE 4096
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struct nmi_seq_buf {
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unsigned char buffer[NMI_BUF_SIZE];
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struct seq_buf seq;
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};
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/* Safe printing in NMI context */
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static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
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/* "in progress" flag of arch_trigger_all_cpu_backtrace */
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static unsigned long backtrace_flag;
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static void print_seq_line(struct nmi_seq_buf *s, int start, int end)
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{
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const char *buf = s->buffer + start;
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printk("%.*s", (end - start) + 1, buf);
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}
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void nmi_trigger_all_cpu_backtrace(bool include_self,
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void (*raise)(cpumask_t *mask))
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{
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struct nmi_seq_buf *s;
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int i, cpu, this_cpu = get_cpu();
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if (test_and_set_bit(0, &backtrace_flag)) {
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/*
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* If there is already a trigger_all_cpu_backtrace() in progress
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* (backtrace_flag == 1), don't output double cpu dump infos.
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*/
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put_cpu();
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return;
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}
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cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
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if (!include_self)
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cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
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cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
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/*
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* Set up per_cpu seq_buf buffers that the NMIs running on the other
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* CPUs will write to.
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*/
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for_each_cpu(cpu, to_cpumask(backtrace_mask)) {
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s = &per_cpu(nmi_print_seq, cpu);
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seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE);
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}
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if (!cpumask_empty(to_cpumask(backtrace_mask))) {
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pr_info("Sending NMI to %s CPUs:\n",
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(include_self ? "all" : "other"));
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raise(to_cpumask(backtrace_mask));
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}
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/* Wait for up to 10 seconds for all CPUs to do the backtrace */
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for (i = 0; i < 10 * 1000; i++) {
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if (cpumask_empty(to_cpumask(backtrace_mask)))
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break;
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mdelay(1);
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touch_softlockup_watchdog();
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}
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/*
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* Now that all the NMIs have triggered, we can dump out their
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* back traces safely to the console.
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*/
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for_each_cpu(cpu, &printtrace_mask) {
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int len, last_i = 0;
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s = &per_cpu(nmi_print_seq, cpu);
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len = seq_buf_used(&s->seq);
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if (!len)
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continue;
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/* Print line by line. */
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for (i = 0; i < len; i++) {
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if (s->buffer[i] == '\n') {
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print_seq_line(s, last_i, i);
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last_i = i + 1;
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}
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}
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/* Check if there was a partial line. */
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if (last_i < len) {
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print_seq_line(s, last_i, len - 1);
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pr_cont("\n");
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}
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}
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clear_bit(0, &backtrace_flag);
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smp_mb__after_atomic();
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put_cpu();
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}
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/*
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* It is not safe to call printk() directly from NMI handlers.
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* It may be fine if the NMI detected a lock up and we have no choice
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* but to do so, but doing a NMI on all other CPUs to get a back trace
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* can be done with a sysrq-l. We don't want that to lock up, which
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* can happen if the NMI interrupts a printk in progress.
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*
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* Instead, we redirect the vprintk() to this nmi_vprintk() that writes
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* the content into a per cpu seq_buf buffer. Then when the NMIs are
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* all done, we can safely dump the contents of the seq_buf to a printk()
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* from a non NMI context.
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*/
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static int nmi_vprintk(const char *fmt, va_list args)
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{
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struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
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unsigned int len = seq_buf_used(&s->seq);
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seq_buf_vprintf(&s->seq, fmt, args);
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return seq_buf_used(&s->seq) - len;
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}
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bool nmi_cpu_backtrace(struct pt_regs *regs)
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{
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int cpu = smp_processor_id();
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if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
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printk_func_t printk_func_save = this_cpu_read(printk_func);
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/* Replace printk to write into the NMI seq */
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this_cpu_write(printk_func, nmi_vprintk);
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pr_warn("NMI backtrace for cpu %d\n", cpu);
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show_regs(regs);
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this_cpu_write(printk_func, printk_func_save);
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cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
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return true;
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}
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return false;
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}
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NOKPROBE_SYMBOL(nmi_cpu_backtrace);
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#endif
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