From: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Date: Thu, 20 May 2010 20:24:24 +0000 (-0400)
Subject: Use spinlock to freeze system for 5 seconds.
X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Fkernel%2Fsamples%2Fchar2%2F.git;a=commitdiff_plain;h=refs%2Fheads%2Fspin

Use spinlock to freeze system for 5 seconds.
---

diff --git a/hellochar.c b/hellochar.c
index a197a1d..180b90c 100644
--- a/hellochar.c
+++ b/hellochar.c
@@ -40,8 +40,10 @@ static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
 	loff_t *pos)
 {
 	unsigned long expire = jiffies + 5 * HZ;
+	spin_lock(&hello_lock);
 	while (time_after(expire, jiffies))
 		cpu_relax();
+	spin_unlock(&hello_lock);
 	return 0;
 }