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Subject[PATCH 2/4] docs: kernel-locking: Convert semaphore references
From
I converted some of the document to reflect mutex usage instead of
semaphore usage. Since we shouldin't be promoting semaphore usage when
it's on it's way out..

Signed-Off-By: Daniel Walker <dwalker@mvista.com>

---
Documentation/DocBook/kernel-locking.tmpl | 32 +++++++++++++++---------------
1 file changed, 16 insertions(+), 16 deletions(-)

Index: linux-2.6.23/Documentation/DocBook/kernel-locking.tmpl
===================================================================
--- linux-2.6.23.orig/Documentation/DocBook/kernel-locking.tmpl
+++ linux-2.6.23/Documentation/DocBook/kernel-locking.tmpl
@@ -717,7 +717,7 @@ used, and when it gets full, throws out
<para>
For our first example, we assume that all operations are in user
context (ie. from system calls), so we can sleep. This means we can
-use a semaphore to protect the cache and all the objects within
+use a mutex to protect the cache and all the objects within
it. Here's the code:
</para>

@@ -725,7 +725,7 @@ it. Here's the code:
#include &lt;linux/list.h&gt;
#include &lt;linux/slab.h&gt;
#include &lt;linux/string.h&gt;
-#include &lt;asm/semaphore.h&gt;
+#include &lt;linux/mutex.h&gt;
#include &lt;asm/errno.h&gt;

struct object
@@ -737,7 +737,7 @@ struct object
};

/* Protects the cache, cache_num, and the objects within it */
-static DECLARE_MUTEX(cache_lock);
+static DEFINE_MUTEX(cache_lock);
static LIST_HEAD(cache);
static unsigned int cache_num = 0;
#define MAX_CACHE_SIZE 10
@@ -789,17 +789,17 @@ int cache_add(int id, const char *name)
obj-&gt;id = id;
obj-&gt;popularity = 0;

- down(&amp;cache_lock);
+ mutex_lock(&amp;cache_lock);
__cache_add(obj);
- up(&amp;cache_lock);
+ mutex_unlock(&amp;cache_lock);
return 0;
}

void cache_delete(int id)
{
- down(&amp;cache_lock);
+ mutex_lock(&amp;cache_lock);
__cache_delete(__cache_find(id));
- up(&amp;cache_lock);
+ mutex_unlock(&amp;cache_lock);
}

int cache_find(int id, char *name)
@@ -807,13 +807,13 @@ int cache_find(int id, char *name)
struct object *obj;
int ret = -ENOENT;

- down(&amp;cache_lock);
+ mutex_lock(&amp;cache_lock);
obj = __cache_find(id);
if (obj) {
ret = 0;
strcpy(name, obj-&gt;name);
}
- up(&amp;cache_lock);
+ mutex_unlock(&amp;cache_lock);
return ret;
}
</programlisting>
@@ -853,7 +853,7 @@ The change is shown below, in standard p
int popularity;
};

--static DECLARE_MUTEX(cache_lock);
+-static DEFINE_MUTEX(cache_lock);
+static spinlock_t cache_lock = SPIN_LOCK_UNLOCKED;
static LIST_HEAD(cache);
static unsigned int cache_num = 0;
@@ -870,22 +870,22 @@ The change is shown below, in standard p
obj-&gt;id = id;
obj-&gt;popularity = 0;

-- down(&amp;cache_lock);
+- mutex_lock(&amp;cache_lock);
+ spin_lock_irqsave(&amp;cache_lock, flags);
__cache_add(obj);
-- up(&amp;cache_lock);
+- mutex_unlock(&amp;cache_lock);
+ spin_unlock_irqrestore(&amp;cache_lock, flags);
return 0;
}

void cache_delete(int id)
{
-- down(&amp;cache_lock);
+- mutex_lock(&amp;cache_lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&amp;cache_lock, flags);
__cache_delete(__cache_find(id));
-- up(&amp;cache_lock);
+- mutex_unlock(&amp;cache_lock);
+ spin_unlock_irqrestore(&amp;cache_lock, flags);
}

@@ -895,14 +895,14 @@ The change is shown below, in standard p
int ret = -ENOENT;
+ unsigned long flags;

-- down(&amp;cache_lock);
+- mutex_lock(&amp;cache_lock);
+ spin_lock_irqsave(&amp;cache_lock, flags);
obj = __cache_find(id);
if (obj) {
ret = 0;
strcpy(name, obj-&gt;name);
}
-- up(&amp;cache_lock);
+- mutex_unlock(&amp;cache_lock);
+ spin_unlock_irqrestore(&amp;cache_lock, flags);
return ret;
}
--


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