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Subject[PATCH 1/6] Fix locking
Date
From: Alan Cox <alan@redhat.com>

Use unlocked_ioctl
Remove semaphores

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
drivers/watchdog/ar7_wdt.c | 29 +++++++++++++++++------------
1 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/watchdog/ar7_wdt.c b/drivers/watchdog/ar7_wdt.c
index 2eb48c0..ef7b0d6 100644
--- a/drivers/watchdog/ar7_wdt.c
+++ b/drivers/watchdog/ar7_wdt.c
@@ -69,7 +69,8 @@ struct ar7_wdt {
u32 prescale;
};

-static struct semaphore open_semaphore;
+static unsigned long wdt_is_open;
+static spinlock_t wdt_lock;
static unsigned expect_close;

/* XXX currently fixed, allows max margin ~68.72 secs */
@@ -154,8 +155,10 @@ static void ar7_wdt_update_margin(int new_margin)
u32 change;

change = new_margin * (ar7_vbus_freq() / prescale_value);
- if (change < 1) change = 1;
- if (change > 0xffff) change = 0xffff;
+ if (change < 1)
+ change = 1;
+ if (change > 0xffff)
+ change = 0xffff;
ar7_wdt_change(change);
margin = change * prescale_value / ar7_vbus_freq();
printk(KERN_INFO DRVNAME
@@ -179,7 +182,7 @@ static void ar7_wdt_disable_wdt(void)
static int ar7_wdt_open(struct inode *inode, struct file *file)
{
/* only allow one at a time */
- if (down_trylock(&open_semaphore))
+ if (test_and_set_bit(0, &wdt_is_open))
return -EBUSY;
ar7_wdt_enable_wdt();
expect_close = 0;
@@ -195,9 +198,7 @@ static int ar7_wdt_release(struct inode *inode, struct file *file)
"will not disable the watchdog timer\n");
else if (!nowayout)
ar7_wdt_disable_wdt();
-
- up(&open_semaphore);
-
+ clear_bit(0, &wdt_is_open);
return 0;
}

@@ -222,7 +223,9 @@ static ssize_t ar7_wdt_write(struct file *file, const char *data,
if (len) {
size_t i;

+ spin_lock(&wdt_lock);
ar7_wdt_kick(1);
+ spin_unlock(&wdt_lock);

expect_close = 0;
for (i = 0; i < len; ++i) {
@@ -237,8 +240,8 @@ static ssize_t ar7_wdt_write(struct file *file, const char *data,
return len;
}

-static int ar7_wdt_ioctl(struct inode *inode, struct file *file,
- unsigned int cmd, unsigned long arg)
+static long ar7_wdt_ioctl(struct file *file,
+ unsigned int cmd, unsigned long arg)
{
static struct watchdog_info ident = {
.identity = LONGNAME,
@@ -269,8 +272,10 @@ static int ar7_wdt_ioctl(struct inode *inode, struct file *file,
if (new_margin < 1)
return -EINVAL;

+ spin_lock(&wdt_lock);
ar7_wdt_update_margin(new_margin);
ar7_wdt_kick(1);
+ spin_unlock(&wdt_lock);

case WDIOC_GETTIMEOUT:
if (put_user(margin, (int *)arg))
@@ -282,7 +287,7 @@ static int ar7_wdt_ioctl(struct inode *inode, struct file *file,
static const struct file_operations ar7_wdt_fops = {
.owner = THIS_MODULE,
.write = ar7_wdt_write,
- .ioctl = ar7_wdt_ioctl,
+ .unlocked_ioctl = ar7_wdt_ioctl,
.open = ar7_wdt_open,
.release = ar7_wdt_release,
};
@@ -297,6 +302,8 @@ static int __init ar7_wdt_init(void)
{
int rc;

+ spin_lock_init(&wdt_lock);
+
ar7_wdt_get_regs();

if (!request_mem_region(ar7_regs_wdt, sizeof(struct ar7_wdt),
@@ -312,8 +319,6 @@ static int __init ar7_wdt_init(void)
ar7_wdt_prescale(prescale_value);
ar7_wdt_update_margin(margin);

- sema_init(&open_semaphore, 1);
-
rc = register_reboot_notifier(&ar7_wdt_notifier);
if (rc) {
printk(KERN_ERR DRVNAME


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