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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>
This commit is contained in:
Arnd Bergmann 2014-01-02 13:07:53 +01:00 committed by Greg Kroah-Hartman
parent 83ce07411d
commit eb831743f2
1 changed files with 4 additions and 1 deletions
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5
drivers/char/nwbutton.c
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@ -168,7 +168,10 @@ static irqreturn_t button_handler (int irq, void *dev_id)
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;
}