1 files changed, 29 insertions, 13 deletions

diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 26caf51cc238..75554754eadf 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -16,21 +16,23 @@
 #include <linux/delay.h>
 #include <linux/kprobes.h>
 #include <linux/nmi.h>
+#include <linux/cpu.h>
 
-#ifdef arch_trigger_all_cpu_backtrace
+#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_all_cpu_backtrace */
+/* "in progress" flag of arch_trigger_cpumask_backtrace */
 static unsigned long backtrace_flag;
 
 /*
- * When raise() is called it will be is passed a pointer to the
+ * 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_all_cpu_backtrace(bool include_self,
+void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
+                                   bool exclude_self,
                                    void (*raise)(cpumask_t *mask))
 {
         int i, this_cpu = get_cpu();
@@ -44,13 +46,22 @@ void nmi_trigger_all_cpu_backtrace(bool include_self,
                 return;
         }
 
-        cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
-        if (!include_self)
+        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 to %s CPUs:\n",
-                        (include_self ? "all" : "other"));
+                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));
         }
 
@@ -77,11 +88,16 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
         int cpu = smp_processor_id();
 
         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
-                pr_warn("NMI backtrace for cpu %d\n", cpu);
-                if (regs)
-                        show_regs(regs);
-                else
-                        dump_stack();
+                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;
         }