[PATCH 5/8] x86/platform/UV: Add basic CPU NMI health check

[Mike Travis]

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 <travis@xxxxxxx>
Acked-by: Dimitri Sivanich <sivanich@xxxxxxx>
Reviewed-by: Russ Anderson <rja@xxxxxxx>
Reviewed-by: Alex Thorlton <athorlton@xxxxxxx>
---
 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 */

--