[PATCH] xen/mce: add .poll method for mcelog device driver

[Liu , Jinsong]

If a driver leaves its poll method NULL, the device is assumed to
be both readable and writable without blocking.

This patch add .poll method to xen mcelog device driver, so that
when mcelog use system calls like ppoll or select, it would be
blocked when no data available, and avoid spinning at CPU.

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
---
 drivers/xen/mcelog.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c
index 804aa3c..c0b39c9 100644
--- a/drivers/xen/mcelog.c
+++ b/drivers/xen/mcelog.c
@@ -41,6 +41,7 @@
 #include <linux/miscdevice.h>
 #include <linux/uaccess.h>
 #include <linux/capability.h>
+#include <linux/poll.h>
=20
 #include <xen/interface/xen.h>
 #include <xen/events.h>
@@ -135,6 +136,14 @@ out:
 	return err ? err : buf - ubuf;
 }
=20
+static unsigned int xen_mce_chrdev_poll(struct file *file, poll_table *wai=
t)
+{
+	if (xen_mcelog.next)
+		return POLLIN | POLLRDNORM;
+
+	return 0;
+}
+
 static long xen_mce_chrdev_ioctl(struct file *f, unsigned int cmd,
 				unsigned long arg)
 {
@@ -166,6 +175,7 @@ static const struct file_operations xen_mce_chrdev_ops =
=3D {
 	.open			=3D xen_mce_chrdev_open,
 	.release		=3D xen_mce_chrdev_release,
 	.read			=3D xen_mce_chrdev_read,
+	.poll			=3D xen_mce_chrdev_poll,
 	.unlocked_ioctl		=3D xen_mce_chrdev_ioctl,
 	.llseek			=3D no_llseek,
 };
--=20
1.7.1

--_002_DE8DF0795D48FD4CA783C40EC82923352321ABSHSMSX101ccrcorpi_
Content-Type: application/octet-stream;
	name="0001-xen-mce-add-.poll-method-for-mcelog-device-driver.patch"
Content-Description: 0001-xen-mce-add-.poll-method-for-mcelog-device-driver.patch
Content-Disposition: attachment;
	filename="0001-xen-mce-add-.poll-method-for-mcelog-device-driver.patch";
	size=1677; creation-date="Thu, 14 Jun 2012 12:49:08 GMT";
	modification-date="Thu, 14 Jun 2012 20:35:18 GMT"
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