staging: add a new "idle_poll" module to disable idle loop

[Willy Tarreau]

Sometimes it's convenient to be able to switch to polled mode for the
idle loop. This module does just that, and reverts back to the original
mode once unloaded.
---
 drivers/staging/Kconfig               |  2 ++
 drivers/staging/Makefile              |  1 +
 drivers/staging/idle_poll/Kconfig     |  8 ++++++++
 drivers/staging/idle_poll/Makefile    |  7 +++++++
 drivers/staging/idle_poll/idle_poll.c | 22 ++++++++++++++++++++++
 kernel/cpu/idle.c                     |  1 +
 6 files changed, 41 insertions(+)
 create mode 100644 drivers/staging/idle_poll/Kconfig
 create mode 100644 drivers/staging/idle_poll/Makefile
 create mode 100644 drivers/staging/idle_poll/idle_poll.c

diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index 9594f204d4fc..936a2721b0f7 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -148,4 +148,6 @@ source "drivers/staging/dgnc/Kconfig"
 
 source "drivers/staging/dgap/Kconfig"
 
+source "drivers/staging/idle_poll/Kconfig"
+
 endif # STAGING
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index 6ca1cf3dbcd4..d3d45aff73d2 100644
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -66,3 +66,4 @@ obj-$(CONFIG_XILLYBUS)		+= xillybus/
 obj-$(CONFIG_DGNC)			+= dgnc/
 obj-$(CONFIG_DGAP)			+= dgap/
 obj-$(CONFIG_MTD_SPINAND_MT29F)	+= mt29f_spinand/
+obj-$(CONFIG_IDLE_POLL)		+= idle_poll/
diff --git a/drivers/staging/idle_poll/Kconfig b/drivers/staging/idle_poll/Kconfig
new file mode 100644
index 000000000000..4c96a21f66aa
--- /dev/null
+++ b/drivers/staging/idle_poll/Kconfig
@@ -0,0 +1,8 @@
+config IDLE_POLL
+	tristate "IDLE_POLL enabler"
+	help
+	    This module automatically enables polling-based idle loop.
+	    It is convenient in certain situations to simply load the
+	    module to disable the idle loop, or unload it to re-enable
+	    it.
+
diff --git a/drivers/staging/idle_poll/Makefile b/drivers/staging/idle_poll/Makefile
new file mode 100644
index 000000000000..60ad176f11f6
--- /dev/null
+++ b/drivers/staging/idle_poll/Makefile
@@ -0,0 +1,7 @@
+# This rule extracts the directory part from the location where this Makefile
+# is found, strips last slash and retrieves the last component which is used
+# to make a file name. It is a generic way of building modules which always
+# have the name of the directory they're located in. $(lastword) could have
+# been used instead of $(word $(words)) but it's bogus on some versions.
+
+obj-m += $(notdir $(patsubst %/,%,$(dir $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))))).o
diff --git a/drivers/staging/idle_poll/idle_poll.c b/drivers/staging/idle_poll/idle_poll.c
new file mode 100644
index 000000000000..6f39f85cc61d
--- /dev/null
+++ b/drivers/staging/idle_poll/idle_poll.c
@@ -0,0 +1,22 @@
+#include <linux/module.h>
+#include <linux/cpu.h>
+
+static int __init modinit(void)
+{
+	cpu_idle_poll_ctrl(true);
+	return 0;
+}
+
+static void __exit modexit(void)
+{
+	cpu_idle_poll_ctrl(false);
+	return;
+}
+
+module_init(modinit);
+module_exit(modexit);
+
+MODULE_DESCRIPTION("idle_poll enabler");
+MODULE_AUTHOR("Willy Tarreau");
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL");
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index 277f494c2a9a..fbf648bc52b2 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -22,6 +22,7 @@ void cpu_idle_poll_ctrl(bool enable)
 		WARN_ON_ONCE(cpu_idle_force_poll < 0);
 	}
 }
+EXPORT_SYMBOL(cpu_idle_poll_ctrl);
 
 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
 static int __init cpu_idle_poll_setup(char *__unused)
-- 
2.20.1