On Fri, 20 Apr 2007 18:11:10 -0400 "David Kyle" <[email protected]> wrote:
> 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?
>
yup, that's a bug. It's not immediately clear to e what driver_lock is
protecting. Some global things, some per-device things, it appears.
A suitable fix might be to make driver_lock a mutex.
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