5 files changed, 55 insertions, 5 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6263a2da3e2f..0231f4508abe 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1269,6 +1269,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
                         Default: 1024
 
+        hardlockup_all_cpu_backtrace=
+                        [KNL] Should the hard-lockup detector generate
+                        backtraces on all cpus.
+                        Format: <integer>
+
         hashdist=       [KNL,NUMA] Large hashes allocated during boot
                         are distributed across NUMA nodes.  Defaults on
                         for 64-bit NUMA, off otherwise.
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 6fccb69c03e7..af70d1541d3a 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -33,6 +33,7 @@ show up in /proc/sys/kernel:
 - domainname
 - hostname
 - hotplug
+- hardlockup_all_cpu_backtrace
 - hung_task_panic
 - hung_task_check_count
 - hung_task_timeout_secs
@@ -293,6 +294,17 @@ domain names are in general different. For a detailed discussion
 see the hostname(1) man page.
 
 ==============================================================
+hardlockup_all_cpu_backtrace:
+
+This value controls the hard lockup detector behavior when a hard
+lockup condition is detected as to whether or not to gather further
+debug information. If enabled, arch-specific all-CPU stack dumping
+will be initiated.
+
+0: do nothing. This is the default behavior.
+
+1: on detection capture more debug information.
+==============================================================
 
 hotplug:
 
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 78488e099ce7..7ec5b86735f3 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -73,6 +73,7 @@ extern int watchdog_user_enabled;
 extern int watchdog_thresh;
 extern unsigned long *watchdog_cpumask_bits;
 extern int sysctl_softlockup_all_cpu_backtrace;
+extern int sysctl_hardlockup_all_cpu_backtrace;
 struct ctl_table;
 extern int proc_watchdog(struct ctl_table *, int ,
                          void __user *, size_t *, loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 96c856b04081..1a5faa3e1521 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -898,6 +898,15 @@ static struct ctl_table kern_table[] = {
                 .extra1         = &zero,
                 .extra2         = &one,
         },
+        {
+                .procname       = "hardlockup_all_cpu_backtrace",
+                .data           = &sysctl_hardlockup_all_cpu_backtrace,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &zero,
+                .extra2         = &one,
+        },
 #endif /* CONFIG_SMP */
 #endif
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 452e4ed507e5..f6b32b8cbffe 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -57,8 +57,10 @@ int __read_mostly watchdog_thresh = 10;
 
 #ifdef CONFIG_SMP
 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
+int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
 #else
 #define sysctl_softlockup_all_cpu_backtrace 0
+#define sysctl_hardlockup_all_cpu_backtrace 0
 #endif
 static struct cpumask watchdog_cpumask __read_mostly;
 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
@@ -112,6 +114,7 @@ static unsigned long soft_lockup_nmi_warn;
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 static int hardlockup_panic =
                         CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
+static unsigned long hardlockup_allcpu_dumped;
 /*
  * We may not want to enable hard lockup detection by default in all cases,
  * for example when running the kernel as a guest on a hypervisor. In these
@@ -173,6 +176,13 @@ static int __init softlockup_all_cpu_backtrace_setup(char *str)
         return 1;
 }
 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
+static int __init hardlockup_all_cpu_backtrace_setup(char *str)
+{
+        sysctl_hardlockup_all_cpu_backtrace =
+                !!simple_strtol(str, NULL, 0);
+        return 1;
+}
+__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
 #endif
 
 /*
@@ -318,17 +328,30 @@ static void watchdog_overflow_callback(struct perf_event *event,
          */
         if (is_hardlockup()) {
                 int this_cpu = smp_processor_id();
+                struct pt_regs *regs = get_irq_regs();
 
                 /* only print hardlockups once */
                 if (__this_cpu_read(hard_watchdog_warn) == true)
                         return;
 
-                if (hardlockup_panic)
-                        panic("Watchdog detected hard LOCKUP on cpu %d",
-                              this_cpu);
+                pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
+                print_modules();
+                print_irqtrace_events(current);
+                if (regs)
+                        show_regs(regs);
                 else
-                        WARN(1, "Watchdog detected hard LOCKUP on cpu %d",
-                             this_cpu);
+                        dump_stack();
+
+                /*
+                 * Perform all-CPU dump only once to avoid multiple hardlockups
+                 * generating interleaving traces
+                 */
+                if (sysctl_hardlockup_all_cpu_backtrace &&
+                                !test_and_set_bit(0, &hardlockup_allcpu_dumped))
+                        trigger_allbutself_cpu_backtrace();
+
+                if (hardlockup_panic)
+                        panic("Hard LOCKUP");
 
                 __this_cpu_write(hard_watchdog_warn, true);
                 return;