Keep track of the time the thread at the head of the secondary queue
has been waiting, and force inter-node handoff once this time passes
a preset threshold. The default value for the threshold (10ms) can be
overridden with the new kernel boot command-line option
"numa_spinlock_threshold". The ms value is translated internally to the
nearest rounded-up jiffies.

Signed-off-by: Alex Kogan <redacted>
Reviewed-by: Steve Sistare <redacted>
Reviewed-by: Waiman Long <longman@redhat.com>
---
 .../admin-guide/kernel-parameters.txt         |  9 ++
 kernel/locking/qspinlock_cna.h                | 95 ++++++++++++++++---
 2 files changed, 92 insertions(+), 12 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 51ce050f8701..73ab23a47b97 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -3363,6 +3363,15 @@
 			Not specifying this option is equivalent to
 			numa_spinlock=auto.
 
+	numa_spinlock_threshold=	[NUMA, PV_OPS]
+			Set the time threshold in milliseconds for the
+			number of intra-node lock hand-offs before the
+			NUMA-aware spinlock is forced to be passed to
+			a thread on another NUMA node.	Valid values
+			are in the [1..100] range. Smaller values result
+			in a more fair, but less performant spinlock,
+			and vice versa. The default value is 10.
+
 	cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
 			CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
 			Some features depend on CPU0. Known dependencies are: