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docs: kernel-locking: Convert semaphore references 

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daniel Walker 2008-02-06 01:37:39 -08:00 committed by Linus Torvalds
parent ec5b1157f8
commit 66656ebb5b
1 changed files with 16 additions and 16 deletions
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32
Documentation/DocBook/kernel-locking.tmpl
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@ -717,7 +717,7 @@ used, and when it gets full, throws out the least used one.
<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 patch format: the
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 patch format: the
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 patch format: the
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;
}