Re: [PATCH 4.19 209/211] fuse: fix deadlock with aio poll and fuse_iqueue::waitq.lock

[Greg Kroah-Hartman]

On Thu, Oct 03, 2019 at 12:48:39PM -0700, Eric Biggers wrote:
> On Thu, Oct 03, 2019 at 05:54:35PM +0200, Greg Kroah-Hartman wrote:
> >  
> >  static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
> >  {
> > -	spin_lock(&fiq->waitq.lock);
> > +	spin_lock(&fiq->lock);
> >  	if (test_bit(FR_FINISHED, &req->flags)) {
> > -		spin_unlock(&fiq->waitq.lock);
> > +		spin_unlock(&fiq->lock);
> >  		return;
> >  	}
> >  	if (list_empty(&req->intr_entry)) {
> >  		list_add_tail(&req->intr_entry, &fiq->interrupts);
> >  		wake_up_locked(&fiq->waitq);
> >  	}
> > -	spin_unlock(&fiq->waitq.lock);
> > +	spin_unlock(&fiq->lock);
> >  	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
> >  }
> 
> This isn't backported correctly.  wake_up_locked() needs to be changed to wake_up().
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index c0d59a86ada2e..6d39143cfa094 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -434,7 +434,7 @@ static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
>  	}
>  	if (list_empty(&req->intr_entry)) {
>  		list_add_tail(&req->intr_entry, &fiq->interrupts);
> -		wake_up_locked(&fiq->waitq);
> +		wake_up(&fiq->waitq);
>  	}
>  	spin_unlock(&fiq->lock);
>  	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);

Thanks for the update and for looking at this.  Now added to the
original patch and pushed out as part of a -rc3.

thanks,

greg k-h