Add a low impact health check triggered by the system NMI command
that essentially checks which CPUs are responding to external NMI's.

Signed-off-by: Mike Travis <tra...@sgi.com>
Acked-by: Dimitri Sivanich <sivan...@hpe.com>
Reviewed-by: Russ Anderson <r...@hpe.com>
Reviewed-by: Alex Thorlton <athorl...@sgi.com>
---
 arch/x86/platform/uv/uv_nmi.c |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

--- linux.orig/arch/x86/platform/uv/uv_nmi.c
+++ linux/arch/x86/platform/uv/uv_nmi.c
@@ -177,6 +177,7 @@ module_param_named(debug, uv_nmi_debug,
  *  "kdump"    - do crash dump
  *  "kdb"      - enter KDB (default)
  *  "kgdb"     - enter KGDB
+ *  "health"   - check if CPUs respond to NMI
  */
 static char uv_nmi_action[8] = "kdb";
 module_param_string(action, uv_nmi_action, sizeof(uv_nmi_action), 0644);
@@ -573,6 +574,22 @@ static void uv_nmi_sync_exit(int master)
        }
 }
 
+/* Current "health" check is which CPU's are responsive */
+static void uv_nmi_action_health(int cpu, struct pt_regs *regs, int master)
+{
+       if (master) {
+               int in = atomic_read(&uv_nmi_cpus_in_nmi);
+               int out = num_online_cpus() - in;
+
+               pr_alert("UV: NMI CPU health check (non-responding:%d)\n", out);
+               atomic_set(&uv_nmi_slave_continue, SLAVE_EXIT);
+       } else {
+               while (!atomic_read(&uv_nmi_slave_continue))
+                       cpu_relax();
+       }
+       uv_nmi_sync_exit(master);
+}
+
 /* Walk through cpu list and dump state of each */
 static void uv_nmi_dump_state(int cpu, struct pt_regs *regs, int master)
 {
@@ -748,8 +765,12 @@ int uv_handle_nmi(unsigned int reason, s
        /* Pause as all cpus enter the NMI handler */
        uv_nmi_wait(master);
 
+       /* Health check for any processors that are 'stuck' */
+       if (uv_nmi_action_is("health"))
+               uv_nmi_action_health(cpu, regs, master);
+
        /* Dump state of each cpu */
-       if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump"))
+       else if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump"))
                uv_nmi_dump_state(cpu, regs, master);
 
        /* Call KGDB/KDB if enabled */

-- 

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