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SubjectRe: [PATCH v3 RESEND 2/2] tpm: add support for nonblocking operation
On Mon, Aug 06, 2018 at 04:05:48PM -0700, James Bottomley wrote:

> > @@ -118,25 +155,48 @@ ssize_t tpm_common_write(struct file *file,
> > const char __user *buf,
> >    * the char dev is held open.
> >    */
> >   if (tpm_try_get_ops(priv->chip)) {
> > - mutex_unlock(&priv->buffer_mutex);
> > - return -EPIPE;
> > + ret = -EPIPE;
> > + goto out;
> >   }
> > - out_size = tpm_transmit(priv->chip, priv->space, priv-
> > >data_buffer,
> > - sizeof(priv->data_buffer), 0);
> >  
> > - tpm_put_ops(priv->chip);
> > - if (out_size < 0) {
> > - mutex_unlock(&priv->buffer_mutex);
> > - return out_size;
> > + /*
> > +  * If in nonblocking mode schedule an async job to send
> > +  * the command return the size.
> > +  * In case of error the err code will be returned in
> > +  * the subsequent read call.
> > +  */
> > + if (file->f_flags & O_NONBLOCK) {
> > + queue_work(tpm_dev_wq, &priv->async_work);
> > + return size;
>
> Here you return holding the buffer_mutex, waiting for tpm_async_work to
> release it.

Doesn't lockdep complain when locks are left held after returning to
user space? Even if it doesn't, that is a pretty ugly thing to do.

Jason

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