Re: [PATCH v2] USB: usbtmc: Fix RCU stall warning

["gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>]

On Tue, Jul 27, 2021 at 07:56:27AM +0000, Guido Kiener wrote:
> > > From: Qiang.zhang>
> > > rcu: INFO: rcu_preempt self-detected stall on CPU
> > > rcu:    1-...!: (2 ticks this GP) idle=d92/1/0x4000000000000000
> > >         softirq=25390/25392 fqs=3
> > >         (t=12164 jiffies g=31645 q=43226)
> > > rcu: rcu_preempt kthread starved for 12162 jiffies! g31645 f0x0
> > >      RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
> > > rcu:    Unless rcu_preempt kthread gets sufficient CPU time,
> > >         OOM is now expected behavior.
> > > rcu: RCU grace-period kthread stack dump:
> > > task:rcu_preempt     state:R  running task
> > > ...........
> > > usbtmc 3-1:0.0: unknown status received: -71 usbtmc 3-1:0.0: unknown
> > > status
> > > received: -71 usbtmc 3-1:0.0: unknown status received: -71 usbtmc 3-1:0.0:
> > > unknown status received: -71 usbtmc 3-1:0.0: unknown status received:
> > > -71 usbtmc
> > > 3-1:0.0: unknown status received: -71 usbtmc 3-1:0.0: unknown status
> > > received: -71 usbtmc 3-1:0.0: unknown status received: -71 usbtmc
> > > 3-1:0.0: usb_submit_urb
> > > failed: -19
> > >
> > > The function usbtmc_interrupt() resubmits urbs when the error status
> > > of an urb is - EPROTO. In systems using the dummy_hcd usb controller
> > > this can result in endless interrupt loops when the usbtmc device is disconnected
> > from the host system.
> > >
> > > Since host controller drivers already try to recover from transmission
> > > errors, there is no need to resubmit the urb or try other solutions to repair the error
> > situation.
> > >
> > > In case of errors the INT pipe just stops to wait for further packets.
> > >
> > > Fixes: dbf3e7f654c0 ("Implement an ioctl to support the USMTMC-USB488
> > > READ_STATUS_BYTE operation")
> > > Cc: stable@vger.kernel.org
> > > Reported-by: syzbot+e2eae5639e7203360018@syzkaller.appspotmail.com
> > > Signed-off-by: Qiang.zhang <qiang.zhang@windriver.com>
> > > ---
> > >  v1->v2:
> > >  Add fixes and stable tags, modify description information.
> > >
> > >  drivers/usb/class/usbtmc.c | 9 +--------
> > >  1 file changed, 1 insertion(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
> > > index
> > > 74d5a9c5238a..73f419adce61 100644
> > > --- a/drivers/usb/class/usbtmc.c
> > > +++ b/drivers/usb/class/usbtmc.c
> > > @@ -2324,17 +2324,10 @@ static void usbtmc_interrupt(struct urb *urb)
> > >  		dev_err(dev, "overflow with length %d, actual length is %d\n",
> > >  			data->iin_wMaxPacketSize, urb->actual_length);
> > >  		fallthrough;
> > > -	case -ECONNRESET:
> > > -	case -ENOENT:
> > > -	case -ESHUTDOWN:
> > > -	case -EILSEQ:
> > > -	case -ETIME:
> > > -	case -EPIPE:
> > > +	default:
> > >  		/* urb terminated, clean up */
> > >  		dev_dbg(dev, "urb terminated, status: %d\n", status);
> > >  		return;
> > > -	default:
> > > -		dev_err(dev, "unknown status received: %d\n", status);
> > >  	}
> > >  exit:
> > >  	rv = usb_submit_urb(urb, GFP_ATOMIC);
> > > --
> > > 2.25.1
> > 
> > The patch looks good to me and is tested on my machine.
> > 
> > Ack-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
> > 
> > -Guido
> 
> Greg,
> 
> Can you please add the patch https://patchwork.kernel.org/project/linux-usb/list/?series=520033
> Dave, Alan, and I are ok with the patch.

Relax, I will get to it :)