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Subject[tip:x86/platform] x86/platform/UV: Add basic CPU NMI health check
Commit-ID:  278c9b099b2fc0cc0a51de95a1dcefcf54ca2183
Gitweb: http://git.kernel.org/tip/278c9b099b2fc0cc0a51de95a1dcefcf54ca2183
Author: travis@sgi.com <travis@sgi.com>
AuthorDate: Wed, 25 Jan 2017 10:35:20 -0600
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 1 Feb 2017 10:20:59 +0100

x86/platform/UV: Add basic CPU NMI health check

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@sgi.com>
Reviewed-by: Russ Anderson <rja@hpe.com>
Reviewed-by: Alex Thorlton <athorlton@sgi.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Dimitri Sivanich <sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170125163517.756690240@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/platform/uv/uv_nmi.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
index df7b092..8a4aa5b 100644
--- a/arch/x86/platform/uv/uv_nmi.c
+++ b/arch/x86/platform/uv/uv_nmi.c
@@ -176,6 +176,7 @@ module_param_named(debug, uv_nmi_debug, int, 0644);
* "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);
@@ -571,6 +572,22 @@ static void uv_nmi_sync_exit(int master)
}
}

+/* Current "health" check is to check 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)
{
@@ -747,7 +764,9 @@ int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
uv_nmi_wait(master);

/* Process actions other than "kdump": */
- if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump")) {
+ if (uv_nmi_action_is("health")) {
+ uv_nmi_action_health(cpu, regs, master);
+ } else if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump")) {
uv_nmi_dump_state(cpu, regs, master);
} else if (uv_nmi_action_is("kdb") || uv_nmi_action_is("kgdb")) {
uv_call_kgdb_kdb(cpu, regs, master);
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