1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c
index 804aa3c181c2..8feee08bcb43 100644
--- a/drivers/xen/mcelog.c
+++ b/drivers/xen/mcelog.c
@@ -41,6 +41,8 @@
 #include <linux/miscdevice.h>
 #include <linux/uaccess.h>
 #include <linux/capability.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
 
 #include <xen/interface/xen.h>
 #include <xen/events.h>
@@ -67,6 +69,8 @@ static DEFINE_SPINLOCK(xen_mce_chrdev_state_lock);
 static int xen_mce_chrdev_open_count;   /* #times opened */
 static int xen_mce_chrdev_open_exclu;   /* already open exclusive? */
 
+static DECLARE_WAIT_QUEUE_HEAD(xen_mce_chrdev_wait);
+
 static int xen_mce_chrdev_open(struct inode *inode, struct file *file)
 {
         spin_lock(&xen_mce_chrdev_state_lock);
@@ -135,6 +139,16 @@ out:
         return err ? err : buf - ubuf;
 }
 
+static unsigned int xen_mce_chrdev_poll(struct file *file, poll_table *wait)
+{
+        poll_wait(file, &xen_mce_chrdev_wait, wait);
+
+        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 +180,7 @@ static const struct file_operations xen_mce_chrdev_ops = {
         .open                   = xen_mce_chrdev_open,
         .release                = xen_mce_chrdev_release,
         .read                   = xen_mce_chrdev_read,
+        .poll                   = xen_mce_chrdev_poll,
         .unlocked_ioctl         = xen_mce_chrdev_ioctl,
         .llseek                 = no_llseek,
 };
@@ -329,6 +344,9 @@ static void xen_mce_work_fn(struct work_struct *work)
                 pr_err(XEN_MCELOG
                        "Failed to handle nonurgent mc_info queue.\n");
 
+        /* wake processes polling /dev/mcelog */
+        wake_up_interruptible(&xen_mce_chrdev_wait);
+
         mutex_unlock(&mcelog_lock);
 }
 static DECLARE_WORK(xen_mce_work, xen_mce_work_fn);