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staging: panel: Fix single-open policy race condition

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Fix the implementation of a single-open policy for both
devices (lcd and keypad) by using atomic_t instead of plain ints.

Signed-off-by: Mariusz Gorski <marius.gorski@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mariusz Gorski 2014-11-04 22:47:19 +01:00 committed by Greg Kroah-Hartman
parent 54fbb2da8d
commit f4757af851
1 changed files with 10 additions and 9 deletions
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19
drivers/staging/panel/panel.c
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@ -404,8 +404,11 @@ static unsigned char lcd_bits[LCD_PORTS][LCD_BITS][BIT_STATES];
#endif /* DEFAULT_PROFILE == 0 */
/* global variables */
static int keypad_open_cnt; /* #times opened */
static int lcd_open_cnt; /* #times opened */
/* Device single-open policy control */
static atomic_t lcd_available = ATOMIC_INIT(1);
static atomic_t keypad_available = ATOMIC_INIT(1);
static struct pardevice *pprt;
static int lcd_initialized;
@ -1347,7 +1350,7 @@ static ssize_t lcd_write(struct file *file,
static int lcd_open(struct inode *inode, struct file *file)
{
if (lcd_open_cnt)
if (!atomic_dec_and_test(&lcd_available))
return -EBUSY; /* open only once at a time */
if (file->f_mode & FMODE_READ) /* device is write-only */
@ -1357,13 +1360,12 @@ static int lcd_open(struct inode *inode, struct file *file)
lcd_clear_display();
lcd_must_clear = 0;
}
lcd_open_cnt++;
return nonseekable_open(inode, file);
}
static int lcd_release(struct inode *inode, struct file *file)
{
lcd_open_cnt--;
atomic_inc(&lcd_available);
return 0;
}
@ -1627,20 +1629,19 @@ static ssize_t keypad_read(struct file *file,
static int keypad_open(struct inode *inode, struct file *file)
{
if (keypad_open_cnt)
if (!atomic_dec_and_test(&keypad_available))
return -EBUSY; /* open only once at a time */
if (file->f_mode & FMODE_WRITE) /* device is read-only */
return -EPERM;
keypad_buflen = 0; /* flush the buffer on opening */
keypad_open_cnt++;
return 0;
}
static int keypad_release(struct inode *inode, struct file *file)
{
keypad_open_cnt--;
atomic_inc(&keypad_available);
return 0;
}
@ -1663,7 +1664,7 @@ static void keypad_send_key(const char *string, int max_len)
return;
/* send the key to the device only if a process is attached to it. */
if (keypad_open_cnt > 0) {
if (!atomic_read(&keypad_available)) {
while (max_len-- && keypad_buflen < KEYPAD_BUFFER && *string) {
keypad_buffer[(keypad_start + keypad_buflen++) %
KEYPAD_BUFFER] = *string++;