Re: [PATCH] use mutex instead of semaphore in tty_io.c

Matthias Kaehlcke
2007-05-31T13:40:51Z

drivers/char/tty_io.c: Use spinlock instead of a (binary) semaphore

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>

--

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 7a32df5..ff27587 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -137,7 +137,7 @@ EXPORT_SYMBOL(tty_mutex);
extern struct tty_driver *ptm_driver; /* Unix98 pty masters; for /dev/ptmx */
extern int pty_limit; /* Config limit on Unix98 ptys */
static DEFINE_IDR(allocated_ptys);
-static DECLARE_MUTEX(allocated_ptys_lock);
+static DEFINE_SPINLOCK(allocated_ptys_lock);
static int ptmx_open(struct inode *, struct file *);
#endif

@@ -2471,9 +2471,9 @@ static void release_dev(struct file * filp)
#ifdef CONFIG_UNIX98_PTYS
/* Make this pty number available for reallocation */
if (devpts) {
- down(&allocated_ptys_lock);
+ spin_lock(&allocated_ptys_lock);
idr_remove(&allocated_ptys, idx);
- up(&allocated_ptys_lock);
+ spin_unlock(&allocated_ptys_lock);
}
#endif

@@ -2639,24 +2639,24 @@ static int ptmx_open(struct inode * inode, struct file * filp)
nonseekable_open(inode, filp);

/* find a device that is not in use. */
- down(&allocated_ptys_lock);
- if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
- up(&allocated_ptys_lock);
+ if (!idr_pre_get(&allocated_ptys, GFP_KERNEL))
return -ENOMEM;
- }
+
+ spin_lock(&allocated_ptys_lock);
+
idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
if (idr_ret < 0) {
- up(&allocated_ptys_lock);
+ spin_unlock(&allocated_ptys_lock);
if (idr_ret == -EAGAIN)
return -ENOMEM;
return -EIO;
}
if (index >= pty_limit) {
idr_remove(&allocated_ptys, index);
- up(&allocated_ptys_lock);
+ spin_unlock(&allocated_ptys_lock);
return -EIO;
}
- up(&allocated_ptys_lock);
+ spin_unlock(&allocated_ptys_lock);

mutex_lock(&tty_mutex);
retval = init_dev(ptm_driver, index, &tty);
@@ -2681,9 +2681,9 @@ out1:
release_dev(filp);
return retval;
out:
- down(&allocated_ptys_lock);
+ spin_lock(&allocated_ptys_lock);
idr_remove(&allocated_ptys, index);
- up(&allocated_ptys_lock);
+ spin_unlock(&allocated_ptys_lock);
return retval;
}
#endif

--
Matthias Kaehlcke
Linux Application Developer
Barcelona

The assumption that what currently exists must necessarily
exist is the acid that corrodes all visionary thinking
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
`. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-