From: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Date: Thu, 20 May 2010 20:22:43 +0000 (-0400)
Subject: Wait 5 seconds testing for jiffies.
X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Fkernel%2Fsamples%2Fchar2%2F.git;a=commitdiff_plain;h=014bb573eed1a3f9c907a4ae6186834e98dbb85c

Wait 5 seconds testing for jiffies.
---

diff --git a/hellochar.c b/hellochar.c
index 206b6d1..a197a1d 100644
--- a/hellochar.c
+++ b/hellochar.c
@@ -21,6 +21,7 @@
 #include <linux/cdev.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/sched.h>
 
 MODULE_LICENSE("GPL");
 
@@ -38,11 +39,9 @@ static int hello_open(struct inode *ino, struct file *fp)
 static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
 	loff_t *pos)
 {
-	int i = 1 << 28;
-	spin_lock(&hello_lock);
-	while (i--)
+	unsigned long expire = jiffies + 5 * HZ;
+	while (time_after(expire, jiffies))
 		cpu_relax();
-	spin_unlock(&hello_lock);
 	return 0;
 }