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Message-ID: <d662ba74-2c02-4298-adfe-f12b3d65471c@rowland.harvard.edu>
Date: Mon, 14 Oct 2024 18:38:32 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+f342ea16c9d06d80b585@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] INFO: task hung in usb_port_suspend
On Mon, Oct 14, 2024 at 11:42:02AM -0700, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
This line in the console log confirms it:
[ 170.681412][ T6529] dummy_hcd dummy_hcd.1: Dequeue norestart: 0 ffff8881067e9700 active 0
Let's add some more debugging info to pin down more closely what's
going wrong.
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";
@@ -257,6 +257,9 @@ struct dummy_hcd {
unsigned active:1;
unsigned old_active:1;
unsigned resuming:1;
+
+ bool alanflag;
+ const char *alandbg;
};
struct dummy {
@@ -1303,9 +1306,11 @@ static int dummy_urb_enqueue(
urb->error_count = 1; /* mark as a new urb */
/* 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),
+ if (!hrtimer_active(&dum_hcd->timer)) {
+ dum_hcd->alandbg = "s1";
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
HRTIMER_MODE_REL_SOFT);
+ }
done:
spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
@@ -1325,9 +1330,19 @@ 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)) {
+ dev_info(dummy_dev(dum_hcd), "Dequeue restart %p\n", urb);
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
+ HRTIMER_MODE_REL_SOFT);
+ dum_hcd->alandbg = "s2";
+ } else {
+ dev_info(dummy_dev(dum_hcd), "Dequeue norestart: %d %d %d %p active %d %s\n",
+ rc, dum_hcd->rh_state,
+ list_empty(&dum_hcd->urbp_list), urb,
+ hrtimer_active(&dum_hcd->timer),
+ dum_hcd->alandbg);
+ }
+ dum_hcd->alanflag = true;
spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
return rc;
}
@@ -1813,10 +1828,14 @@ static enum hrtimer_restart dummy_timer(
/* look at each urb queued by the host side driver */
spin_lock_irqsave(&dum->lock, flags);
+ dum_hcd->alandbg = "cb1";
+ if (dum_hcd->alanflag)
+ dev_info(dummy_dev(dum_hcd), "Timer handler\n");
if (!dum_hcd->udev) {
dev_err(dummy_dev(dum_hcd),
"timer fired with no URBs pending?\n");
+ dum_hcd->alandbg = "cb2";
spin_unlock_irqrestore(&dum->lock, flags);
return HRTIMER_NORESTART;
}
@@ -1984,6 +2003,8 @@ return_urb:
ep->already_seen = ep->setup_stage = 0;
usb_hcd_unlink_urb_from_ep(dummy_hcd_to_hcd(dum_hcd), urb);
+ if (dum_hcd->alanflag)
+ dev_info(dummy_dev(dum_hcd), "Giveback %p\n", urb);
spin_unlock(&dum->lock);
usb_hcd_giveback_urb(dummy_hcd_to_hcd(dum_hcd), urb, status);
spin_lock(&dum->lock);
@@ -1994,12 +2015,15 @@ return_urb:
if (list_empty(&dum_hcd->urbp_list)) {
usb_put_dev(dum_hcd->udev);
dum_hcd->udev = NULL;
+ dum_hcd->alandbg = "cb3";
} 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),
+ dum_hcd->alandbg = "scb";
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
HRTIMER_MODE_REL_SOFT);
- }
+ } else
+ dum_hcd->alandbg = "cb4";
+ dum_hcd->alanflag = false;
spin_unlock_irqrestore(&dum->lock, flags);
return HRTIMER_NORESTART;
@@ -2390,8 +2414,11 @@ static int dummy_bus_resume(struct usb_h
} else {
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);
+ if (!list_empty(&dum_hcd->urbp_list)) {
+ dum_hcd->alandbg = "s3";
+ hrtimer_start(&dum_hcd->timer, DUMMY_INT_KTIME,
+ HRTIMER_MODE_REL_SOFT);
+ }
hcd->state = HC_STATE_RUNNING;
}
spin_unlock_irq(&dum_hcd->dum->lock);
@@ -2490,6 +2517,7 @@ static int dummy_start(struct usb_hcd *h
{
struct dummy_hcd *dum_hcd = hcd_to_dummy_hcd(hcd);
+ dum_hcd->alandbg = "i";
/*
* HOST side init ... we emulate a root hub that'll only ever
* talk to one device (the gadget side). Also appears in sysfs,
@@ -2521,6 +2549,7 @@ static void dummy_stop(struct usb_hcd *h
{
struct dummy_hcd *dum_hcd = hcd_to_dummy_hcd(hcd);
+ dum_hcd->alandbg = "can";
hrtimer_cancel(&dum_hcd->timer);
device_remove_file(dummy_dev(dum_hcd), &dev_attr_urbs);
dev_info(dummy_dev(dum_hcd), "stopped\n");
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