#endif
#ifdef arch_trigger_all_cpu_backtrace
-/* For reliability, we're prepared to waste bits here. */
-static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
-static cpumask_t printtrace_mask;
-
-#define NMI_BUF_SIZE 4096
-
-struct nmi_seq_buf {
- unsigned char buffer[NMI_BUF_SIZE];
- struct seq_buf seq;
-};
-
-/* Safe printing in NMI context */
-static DEFINE_PER_CPU(struct nmi_seq_buf, nmi_print_seq);
-
-/* "in progress" flag of arch_trigger_all_cpu_backtrace */
-static unsigned long backtrace_flag;
-
-static void print_seq_line(struct nmi_seq_buf *s, int start, int end)
+static void nmi_raise_cpu_backtrace(cpumask_t *mask)
{
- const char *buf = s->buffer + start;
-
- printk("%.*s", (end - start) + 1, buf);
+ apic->send_IPI_mask(mask, NMI_VECTOR);
}
void arch_trigger_all_cpu_backtrace(bool include_self)
{
- struct nmi_seq_buf *s;
- int len;
- int cpu;
- int i;
- int 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), cpu_online_mask);
- if (!include_self)
- cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
-
- cpumask_copy(&printtrace_mask, to_cpumask(backtrace_mask));
- /*
- * Set up per_cpu seq_buf buffers that the NMIs running on the other
- * CPUs will write to.
- */
- for_each_cpu(cpu, to_cpumask(backtrace_mask)) {
- s = &per_cpu(nmi_print_seq, cpu);
- seq_buf_init(&s->seq, s->buffer, NMI_BUF_SIZE);
- }
-
- if (!cpumask_empty(to_cpumask(backtrace_mask))) {
- pr_info("sending NMI to %s CPUs:\n",
- (include_self ? "all" : "other"));
- apic->send_IPI_mask(to_cpumask(backtrace_mask), NMI_VECTOR);
- }
-
- /* 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();
- }
-
- /*
- * Now that all the NMIs have triggered, we can dump out their
- * back traces safely to the console.
- */
- for_each_cpu(cpu, &printtrace_mask) {
- int last_i = 0;
-
- s = &per_cpu(nmi_print_seq, cpu);
- len = seq_buf_used(&s->seq);
- if (!len)
- continue;
-
- /* Print line by line. */
- for (i = 0; i < len; i++) {
- if (s->buffer[i] == '\n') {
- print_seq_line(s, last_i, i);
- last_i = i + 1;
- }
- }
- /* Check if there was a partial line. */
- if (last_i < len) {
- print_seq_line(s, last_i, len - 1);
- pr_cont("\n");
- }
- }
-
- clear_bit(0, &backtrace_flag);
- smp_mb__after_atomic();
- put_cpu();
-}
-
-/*
- * It is not safe to call printk() directly from NMI handlers.
- * It may be fine if the NMI detected a lock up and we have no choice
- * but to do so, but doing a NMI on all other CPUs to get a back trace
- * can be done with a sysrq-l. We don't want that to lock up, which
- * can happen if the NMI interrupts a printk in progress.
- *
- * Instead, we redirect the vprintk() to this nmi_vprintk() that writes
- * the content into a per cpu seq_buf buffer. Then when the NMIs are
- * all done, we can safely dump the contents of the seq_buf to a printk()
- * from a non NMI context.
- */
-static int nmi_vprintk(const char *fmt, va_list args)
-{
- struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
- unsigned int len = seq_buf_used(&s->seq);
-
- seq_buf_vprintf(&s->seq, fmt, args);
- return seq_buf_used(&s->seq) - len;
+ nmi_trigger_all_cpu_backtrace(include_self, nmi_raise_cpu_backtrace);
}
static int
arch_trigger_all_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
{
- int cpu;
-
- cpu = smp_processor_id();
-
- if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
- printk_func_t printk_func_save = this_cpu_read(printk_func);
-
- /* Replace printk to write into the NMI seq */
- this_cpu_write(printk_func, nmi_vprintk);
- printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
- show_regs(regs);
- this_cpu_write(printk_func, printk_func_save);
-
- cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
+ if (nmi_cpu_backtrace(regs))
return NMI_HANDLED;
- }
return NMI_DONE;
}
Code Review / kvmfornfv.git / blobdiff