From: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Date: Mon, 24 May 2010 12:51:31 +0000 (-0400)
Subject: Use completion.
X-Git-Url: http://git.cascardo.info/?p=cascardo%2Fkernel%2Fsamples%2Fchar2%2F.git;a=commitdiff_plain;h=10c2d46c6408882fd1eec0b1d59a5dec086040c2

Use completion.
---

diff --git a/hellochar.c b/hellochar.c
index a22677d..a847392 100644
--- a/hellochar.c
+++ b/hellochar.c
@@ -23,6 +23,8 @@
 #include <linux/mutex.h>
 #include <asm/uaccess.h>
 #include <linux/circ_buf.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
 
 MODULE_LICENSE("GPL");
 
@@ -34,6 +36,7 @@ static const char default_greeting[] = "Hello, World!\n";
 static struct circ_buf *hello;
 static struct circ_buf hello_instance;
 static DEFINE_MUTEX(hello_mtx);
+static DECLARE_COMPLETION(hello_wait);
 
 static int hello_open(struct inode *ino, struct file *fp)
 {
@@ -63,6 +66,7 @@ static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
 	mutex_unlock(&hello_mtx);
 	if (r)
 		return -EFAULT;
+	complete(&hello_wait);
 	return sz;
 }
 
@@ -76,6 +80,14 @@ static ssize_t hello_write(struct file *fp, const char __user *buf, size_t sz,
 	if (mutex_lock_interruptible(&hello_mtx))
 		return -ERESTARTSYS;
 	len = CIRC_SPACE(hello->head, hello->tail, MAXLEN);
+	while (len == 0) {
+		mutex_unlock(&hello_mtx);
+		if (wait_for_completion_interruptible(&hello_wait))
+			return -ERESTARTSYS;
+		if (mutex_lock_interruptible(&hello_mtx))
+			return -ERESTARTSYS;
+		len = CIRC_SPACE(hello->head, hello->tail, MAXLEN);
+	}
 	if (sz > len)
 		sz = len;
 	fsz = min(sz, CIRC_SPACE_TO_END(hello->head, hello->tail, MAXLEN));