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Message-ID: <d6ec3898-b225-4c92-a381-46b111b6ddcf@rowland.harvard.edu>
Date: Sat, 12 Oct 2024 22:43:13 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+f342ea16c9d06d80b585@...kaller.appspotmail.com>
Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
linux-usb@...r.kernel.org, sylv@...v.io,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] INFO: task hung in usb_port_suspend
On Sat, Oct 12, 2024 at 07:10:05PM -0700, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> INFO: task hung in usb_register_dev
The console log shows a lot of dequeue failures. Let's find out why
they are failing.
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";
@@ -276,6 +276,7 @@ struct dummy {
unsigned ints_enabled:1;
unsigned udc_suspended:1;
unsigned pullup:1;
+ bool alanflag;
/*
* HOST side support
@@ -1304,7 +1305,7 @@ 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:
@@ -1325,9 +1326,15 @@ 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);
-
+ !list_empty(&dum_hcd->urbp_list)) {
+ dum_hcd->dum->alanflag = true;
+ dev_info(udc_dev(dum_hcd->dum), "Dequeue %p\n", urb);
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
+ HRTIMER_MODE_REL_SOFT);
+ } else
+ dev_info(udc_dev(dum_hcd->dum), "Failed dequeue: %d %d %d\n",
+ rc, dum_hcd->rh_state,
+ list_empty(&dum_hcd->urbp_list));
spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
return rc;
}
@@ -1788,6 +1795,7 @@ static enum hrtimer_restart dummy_timer(
unsigned long flags;
int limit, total;
int i;
+ int alancnt = 0;
/* simplistic model for one frame's bandwidth */
/* FIXME: account for transaction and packet overhead */
@@ -1984,6 +1992,9 @@ return_urb:
ep->already_seen = ep->setup_stage = 0;
usb_hcd_unlink_urb_from_ep(dummy_hcd_to_hcd(dum_hcd), urb);
+ if (dum->alanflag)
+ dev_info(udc_dev(dum), "Give back %p\n", urb);
+ ++alancnt;
spin_unlock(&dum->lock);
usb_hcd_giveback_urb(dummy_hcd_to_hcd(dum_hcd), urb, status);
spin_lock(&dum->lock);
@@ -1995,11 +2006,14 @@ 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);
}
+ if (dum->alanflag) {
+ dev_info(udc_dev(dum), "Gave back %d URBs\n", alancnt);
+ dum->alanflag = false;
+ }
spin_unlock_irqrestore(&dum->lock, flags);
return HRTIMER_NORESTART;
@@ -2391,7 +2405,8 @@ 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);
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