Re: [syzbot] Re: [syzbot] [usb?] INFO: rcu detected stall in schedule_timeout (6)

[syzbot <syzbot+c793a7eca38803212c61@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [usb?] INFO: rcu detected stall in schedule_timeout (6)
Author: marcello.bauer@9elements.com

#syz test

--- 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;

On Thu, 2024-05-16 at 15:01 -0700, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit a7f3813e589fd8e2834720829a47b5eb914a9afe
> Author: Marcello Sylvester Bauer <sylv@sylv.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=119318d0980000
> start commit:   75fa778d74b7 Add linux-next specific files for
> 20240510
> git tree:       linux-next
> final oops:    
> https://syzkaller.appspot.com/x/report.txt?x=139318d0980000
> console output:
> https://syzkaller.appspot.com/x/log.txt?x=159318d0980000
> kernel config: 
> https://syzkaller.appspot.com/x/.config?x=ccdd3ebd6715749a
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=c793a7eca38803212c61
> syz repro:     
> https://syzkaller.appspot.com/x/repro.syz?x=16dcd598980000
> C reproducer:  
> https://syzkaller.appspot.com/x/repro.c?x=151d9c78980000
> 
> Reported-by: syzbot+c793a7eca38803212c61@syzkaller.appspotmail.com
> Fixes: a7f3813e589f ("usb: gadget: dummy_hcd: Switch to hrtimer
> transfer scheduler")
> 
> For information about bisection process see:
> https://goo.gl/tpsmEJ#bisection

-- 
 
 

  

    Marcello Sylvester Bauer
    

    Senior Linux Solutions Architect
    

  

  


  

  

    

      
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