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SubjectRe: [PATCH]: Factor out PTY index allocation
On Wed, 16 Apr 2008 15:17:23 -0700
sukadev@us.ibm.com wrote:

> Factor out the code used to allocate/free a pts index into new interfaces,
> devpts_new_index() and devpts_kill_index(). This localizes the external
> data structures used in managing the pts indices.

err...

> - mutex_lock(&allocated_ptys_lock);
> + down(&allocated_ptys_lock);

Why the mutex-to-semaphore conversion?


--- a/fs/devpts/inode.c~devpts-factor-out-pty-index-allocation-fix
+++ a/fs/devpts/inode.c
@@ -17,6 +17,7 @@
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
+#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
@@ -29,7 +30,7 @@

extern int pty_limit; /* Config limit on Unix98 ptys */
static DEFINE_IDR(allocated_ptys);
-static DECLARE_MUTEX(allocated_ptys_lock);
+static DEFINE_MUTEX(allocated_ptys_lock);

static struct vfsmount *devpts_mnt;
static struct dentry *devpts_root;
@@ -186,10 +187,10 @@ retry:
return -ENOMEM;
}

- down(&allocated_ptys_lock);
+ mutex_lock(&allocated_ptys_lock);
idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
if (idr_ret < 0) {
- up(&allocated_ptys_lock);
+ mutex_unlock(&allocated_ptys_lock);
if (idr_ret == -EAGAIN)
goto retry;
return -EIO;
@@ -197,18 +198,18 @@ retry:

if (index >= pty_limit) {
idr_remove(&allocated_ptys, index);
- up(&allocated_ptys_lock);
+ mutex_unlock(&allocated_ptys_lock);
return -EIO;
}
- up(&allocated_ptys_lock);
+ mutex_unlock(&allocated_ptys_lock);
return index;
}

void devpts_kill_index(int idx)
{
- down(&allocated_ptys_lock);
+ mutex_lock(&allocated_ptys_lock);
idr_remove(&allocated_ptys, idx);
- up(&allocated_ptys_lock);
+ mutex_unlock(&allocated_ptys_lock);
}

int devpts_pty_new(struct tty_struct *tty)
_


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