+ x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation.patch added to -mm tree

+ x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation.patch added to -mm tree

[akpm]

The patch titled
     x86_64: inhibit machine from asserting an NMI when doing Alt-SysRq-M operation
has been added to the -mm tree.  Its filename is
     x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation.patch

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: x86_64: inhibit machine from asserting an NMI when doing Alt-SysRq-M operation
From: Konrad Rzeszutek <konrad@darnok.org>

Touch the NMI watchdog to inhibit the machine from triggering an NMI while
the CPUs are locked.  This situation is happening on boxes with more than
64CPUs and 128GB of RAM when Alt-SysRq-m is performed.

It has been succesfully tested for regression on uni, 2, 4, 8 32, and 64
CPU boxes with various memory configuration.

Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86_64/mm/init.c |    6 ++++++
 1 files changed, 6 insertions(+)

diff -puN arch/x86_64/mm/init.c~x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation arch/x86_64/mm/init.c
--- a/arch/x86_64/mm/init.c~x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation
+++ a/arch/x86_64/mm/init.c
@@ -26,6 +26,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/memory_hotplug.h>
+#include <linux/nmi.h>
 
 #include <asm/processor.h>
 #include <asm/system.h>
@@ -72,6 +73,11 @@ void show_mem(void)
 
 	for_each_online_pgdat(pgdat) {
                for (i = 0; i < pgdat->node_spanned_pages; ++i) {
+			/* this loop can take a while with 256 GB and 4k pages
+			   so update the NMI watchdog */
+			if (unlikely(i % MAX_ORDER_NR_PAGES == 0)) {
+				touch_nmi_watchdog();
+			}
 			page = pfn_to_page(pgdat->node_start_pfn + i);
 			total++;
 			if (PageReserved(page))
_

Patches currently in -mm which might be from konrad@darnok.org are

x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation.patch
x86_64-inhibit-machine-from-asserting-an-nmi-when-doing-alt-sysrq-m-operation-tidy.patch