linux-kernel - Re: [syzbot] [usb?] INFO: task hung in uevent

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Message-ID: <ade15714-6aa3-4988-8b45-719fc9d74727@rowland.harvard.edu>
Date: Tue, 23 Jul 2024 11:30:04 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+edd9fe0d3a65b14588d5@...kaller.appspotmail.com>
Cc: andriy.shevchenko@...ux.intel.com, f.fainelli@...il.com,
	fancer.lancer@...il.com, gregkh@...uxfoundation.org,
	ilpo.jarvinen@...ux.intel.com, jirislaby@...nel.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-usb@...r.kernel.org, marcello.bauer@...ements.com,
	rafael@...nel.org, sylv@...v.io, syzkaller-bugs@...glegroups.com,
	tglx@...utronix.de
Subject: Re: [syzbot] [usb?] INFO: task hung in uevent_show

On Sun, Jul 21, 2024 at 06:36:01AM -0700, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit a7f3813e589fd8e2834720829a47b5eb914a9afe
> Author: Marcello Sylvester Bauer <sylv@...v.io>
> Date:   Thu Apr 11 14:51:28 2024 +0000
> 
>     usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12d54f2d980000
> start commit:   d35b2284e966 Add linux-next specific files for 20240607
> git tree:       linux-next
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=11d54f2d980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=16d54f2d980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d8bf5cd6bcca7343
> dashboard link: https://syzkaller.appspot.com/bug?extid=edd9fe0d3a65b14588d5
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10905c26980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1122da8c980000
> 
> Reported-by: syzbot+edd9fe0d3a65b14588d5@...kaller.appspotmail.com
> Fixes: a7f3813e589f ("usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Let's try again to see if Marcello's patch fixes the problem.  The first 
try had a typo.

Alan Stern

#syz test: linux-next d35b2284e966

--- a/drivers/usb/gadget/udc/dummy_hcd.c
+++ b/drivers/usb/gadget/udc/dummy_hcd.c
@@ -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_MODE_REL);
+		hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS), HRTIMER_MODE_REL_SOFT);
 
  done:
 	spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
@@ -1325,7 +1325,7 @@ static int dummy_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 	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);
+		hrtimer_start(&dum_hcd->timer, ns_to_ktime(0), HRTIMER_MODE_REL_SOFT);
 
 	spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
 	return rc;
@@ -1995,7 +1995,7 @@ static enum hrtimer_restart dummy_timer(struct hrtimer *t)
 		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_MODE_REL);
+		hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS), HRTIMER_MODE_REL_SOFT);
 	}
 
 	spin_unlock_irqrestore(&dum->lock, flags);
@@ -2389,7 +2389,7 @@ static int dummy_bus_resume(struct usb_hcd *hcd)
 		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);
+			hrtimer_start(&dum_hcd->timer, ns_to_ktime(0), HRTIMER_MODE_REL_SOFT);
 		hcd->state = HC_STATE_RUNNING;
 	}
 	spin_unlock_irq(&dum_hcd->dum->lock);
@@ -2467,7 +2467,7 @@ static DEVICE_ATTR_RO(urbs);
 
 static int dummy_start_ss(struct dummy_hcd *dum_hcd)
 {
-	hrtimer_init(&dum_hcd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_init(&dum_hcd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
 	dum_hcd->timer.function = dummy_timer;
 	dum_hcd->rh_state = DUMMY_RH_RUNNING;
 	dum_hcd->stream_en_ep = 0;
@@ -2497,7 +2497,7 @@ static int dummy_start(struct usb_hcd *hcd)
 		return dummy_start_ss(dum_hcd);
 
 	spin_lock_init(&dum_hcd->dum->lock);
-	hrtimer_init(&dum_hcd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_init(&dum_hcd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
 	dum_hcd->timer.function = dummy_timer;
 	dum_hcd->rh_state = DUMMY_RH_RUNNING;
 
-- 
2.45.2