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

[Guido Kiener <Guido.Kiener@rohde-schwarz.com>]

> > 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.

-Guido