Sleep during spinlock in TPM driver

["David Kyle" <dsk6@pitt.edu>]

I've been working with the TPM driver, and I found that if I opened,
used, then closed the TPM char device very frequently, I would get a
kernel BUG message saying that the kernel tried to sleep while holding
a spinlock.  I think I've isolated the problem to this function, in
drivers/char/tpm/tpm.c:

int tpm_release(struct inode *inode, struct file *file)
{
       struct tpm_chip *chip = file->private_data;
       spin_lock(&driver_lock);
       file->private_data = NULL;
       chip->num_opens--;
       del_singleshot_timer_sync(&chip->user_read_timer);
       flush_scheduled_work();
       atomic_set(&chip->data_pending, 0);
       put_device(chip->dev);
       kfree(chip->data_buffer);
       spin_unlock(&driver_lock);
       return 0;
}
EXPORT_SYMBOL_GPL(tpm_release);

I believe that flush_scheduled_work can sleep, correct?  Does anyone
know why this function is called while the spinlock is held?

-David
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