Re: [syzbot] [usb?] INFO: task hung in usb_port_suspend

Alan Stern
2024-10-12T00:48:31Z

On Fri, Oct 11, 2024 at 08:45:03AM -0700, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>
> Reported-by: syzbot+f342ea16c9d06d80b585@syzkaller.appspotmail.com
> Tested-by: syzbot+f342ea16c9d06d80b585@syzkaller.appspotmail.com
>
> Tested on:
>
> commit: 4a9fe2a8 dt-bindings: usb: dwc3-imx8mp: add compatible..
> git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> console output: https://syzkaller.appspot.com/x/log.txt?x=15346f07980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4510af5d637450fb
> dashboard link: https://syzkaller.appspot.com/bug?extid=f342ea16c9d06d80b585
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> patch: https://syzkaller.appspot.com/x/patch.diff?x=1456db27980000
>
> Note: testing is done by a robot and is best-effort only.

Maybe the problem occurs because the hrtimer subsystem doesn't like
timeouts set to the current moment. Let's try changing them all to be
in the future.

Alan Stern

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing

Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c
+++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
@@ -50,7 +50,7 @@
#define POWER_BUDGET 500 /* in mA; use 8 for low-power port testing */
#define POWER_BUDGET_3 900 /* in mA */

-#define DUMMY_TIMER_INT_NSECS 125000 /* 1 microframe */
+#define DUMMY_INT_KTIME ns_to_ktime(125000) /* 1 microframe */

static const char driver_name[] = "dummy_hcd";
static const char driver_desc[] = "USB Host+Gadget Emulator";
@@ -1304,7 +1304,7 @@ static int dummy_urb_enqueue(

/* kick the scheduler, it'll do the rest */
if (!hrtimer_active(&dum_hcd->timer))
- hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS),
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
HRTIMER_MODE_REL_SOFT);

done:
@@ -1326,7 +1326,8 @@ static int dummy_urb_dequeue(struct usb_
rc = usb_hcd_check_unlink_urb(hcd, urb, status);
if (!rc && dum_hcd->rh_state != DUMMY_RH_RUNNING &&
!list_empty(&dum_hcd->urbp_list))
- hrtimer_start(&dum_hcd->timer, ns_to_ktime(0), HRTIMER_MODE_REL_SOFT);
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
+ HRTIMER_MODE_REL_SOFT);

spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
return rc;
@@ -1995,8 +1996,7 @@ return_urb:
usb_put_dev(dum_hcd->udev);
dum_hcd->udev = NULL;
} else if (dum_hcd->rh_state == DUMMY_RH_RUNNING) {
- /* want a 1 msec delay here */
- hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS),
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
HRTIMER_MODE_REL_SOFT);
}

@@ -2391,7 +2391,8 @@ static int dummy_bus_resume(struct usb_h
dum_hcd->rh_state = DUMMY_RH_RUNNING;
set_link_state(dum_hcd);
if (!list_empty(&dum_hcd->urbp_list))
- hrtimer_start(&dum_hcd->timer, ns_to_ktime(0), HRTIMER_MODE_REL_SOFT);
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
+ HRTIMER_MODE_REL_SOFT);
hcd->state = HC_STATE_RUNNING;
}
spin_unlock_irq(&dum_hcd->dum->lock);