char: nwbutton: open-code interruptible_sleep_on
The nwbutton driver uses interruptible_sleep_on to wait for buttons
getting pressed after we enter the read() function, which is inherently
racy and cannot be fixed by using wait_event without changing the
driver's user space interface.
Instead, this patch just uses an open-coded variant of the same
interruptible_sleep_on() call, so the driver behavior doesn't change
but we remove the sleep_on family from the kernel.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/char/nwbutton.c b/drivers/char/nwbutton.c
index 1fd00dc0..76c490f 100644
--- a/drivers/char/nwbutton.c
+++ b/drivers/char/nwbutton.c
@@ -168,7 +168,10 @@
static int button_read (struct file *filp, char __user *buffer,
size_t count, loff_t *ppos)
{
- interruptible_sleep_on (&button_wait_queue);
+ DEFINE_WAIT(wait);
+ prepare_to_wait(&button_wait_queue, &wait, TASK_INTERRUPTIBLE);
+ schedule();
+ finish_wait(&button_wait_queue, &wait);
return (copy_to_user (buffer, &button_output_buffer, bcount))
? -EFAULT : bcount;
}