usb: mon: Make mon_bus::lock a raw spinlock

[PATCH] usb: mon: Make mon_bus::lock a raw spinlock

Posted by Lizhi Xu 2 weeks, 3 days ago

Interrupts are disabled before entering usb_hcd_giveback_urb().
A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
acquired with disabled interrupts.

Make mon_bus::lock a raw spinlock so it can be used with interrupts disabled.

syz reported:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
CPU: 1 UID: 0 PID: 45 Comm: kworker/1:1 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x44b/0x5d0 kernel/sched/core.c:8957
 rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:44 [inline]
 mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
 mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
 usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
 __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
 vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818

Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 drivers/usb/mon/mon_main.c | 24 +++++++++---------------
 drivers/usb/mon/mon_text.c |  6 +++---
 drivers/usb/mon/usb_mon.h  |  2 +-
 3 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/drivers/usb/mon/mon_main.c b/drivers/usb/mon/mon_main.c
index af852d53aac6..83d19b769d84 100644
--- a/drivers/usb/mon/mon_main.c
+++ b/drivers/usb/mon/mon_main.c
@@ -38,7 +38,7 @@ void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
 	unsigned long flags;
 	struct list_head *p;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	raw_spin_lock_irqsave(&mbus->lock, flags);
 	if (mbus->nreaders == 0) {
 		if (mbus == &mon_bus0) {
 			list_for_each (p, &mon_buses) {
@@ -52,7 +52,7 @@ void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
 	}
 	mbus->nreaders++;
 	list_add_tail(&r->r_link, &mbus->r_list);
-	spin_unlock_irqrestore(&mbus->lock, flags);
+	raw_spin_unlock_irqrestore(&mbus->lock, flags);
 
 	kref_get(&mbus->ref);
 }
@@ -66,12 +66,12 @@ void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	raw_spin_lock_irqsave(&mbus->lock, flags);
 	list_del(&r->r_link);
 	--mbus->nreaders;
 	if (mbus->nreaders == 0)
 		mon_stop(mbus);
-	spin_unlock_irqrestore(&mbus->lock, flags);
+	raw_spin_unlock_irqrestore(&mbus->lock, flags);
 
 	kref_put(&mbus->ref, mon_bus_drop);
 }
@@ -80,14 +80,12 @@ void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
  */
 static void mon_bus_submit(struct mon_bus *mbus, struct urb *urb)
 {
-	unsigned long flags;
 	struct mon_reader *r;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	guard(raw_spinlock_irqsave)(&mbus->lock);
 	mbus->cnt_events++;
 	list_for_each_entry(r, &mbus->r_list, r_link)
 		r->rnf_submit(r->r_data, urb);
-	spin_unlock_irqrestore(&mbus->lock, flags);
 }
 
 static void mon_submit(struct usb_bus *ubus, struct urb *urb)
@@ -104,14 +102,12 @@ static void mon_submit(struct usb_bus *ubus, struct urb *urb)
  */
 static void mon_bus_submit_error(struct mon_bus *mbus, struct urb *urb, int error)
 {
-	unsigned long flags;
 	struct mon_reader *r;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	guard(raw_spinlock_irqsave)(&mbus->lock);
 	mbus->cnt_events++;
 	list_for_each_entry(r, &mbus->r_list, r_link)
 		r->rnf_error(r->r_data, urb, error);
-	spin_unlock_irqrestore(&mbus->lock, flags);
 }
 
 static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
@@ -128,14 +124,12 @@ static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
  */
 static void mon_bus_complete(struct mon_bus *mbus, struct urb *urb, int status)
 {
-	unsigned long flags;
 	struct mon_reader *r;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	guard(raw_spinlock_irqsave)(&mbus->lock);
 	mbus->cnt_events++;
 	list_for_each_entry(r, &mbus->r_list, r_link)
 		r->rnf_complete(r->r_data, urb, status);
-	spin_unlock_irqrestore(&mbus->lock, flags);
 }
 
 static void mon_complete(struct usb_bus *ubus, struct urb *urb, int status)
@@ -277,7 +271,7 @@ static void mon_bus_init(struct usb_bus *ubus)
 	if (mbus == NULL)
 		goto err_alloc;
 	kref_init(&mbus->ref);
-	spin_lock_init(&mbus->lock);
+	raw_spin_lock_init(&mbus->lock);
 	INIT_LIST_HEAD(&mbus->r_list);
 
 	/*
@@ -304,7 +298,7 @@ static void mon_bus0_init(void)
 	struct mon_bus *mbus = &mon_bus0;
 
 	kref_init(&mbus->ref);
-	spin_lock_init(&mbus->lock);
+	raw_spin_lock_init(&mbus->lock);
 	INIT_LIST_HEAD(&mbus->r_list);
 
 	mbus->text_inited = mon_text_add(mbus, NULL);
diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index 68b9b2b41189..b482c610dad1 100644
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -307,15 +307,15 @@ static struct mon_event_text *mon_text_fetch(struct mon_reader_text *rp,
 	struct list_head *p;
 	unsigned long flags;
 
-	spin_lock_irqsave(&mbus->lock, flags);
+	raw_spin_lock_irqsave(&mbus->lock, flags);
 	if (list_empty(&rp->e_list)) {
-		spin_unlock_irqrestore(&mbus->lock, flags);
+		raw_spin_unlock_irqrestore(&mbus->lock, flags);
 		return NULL;
 	}
 	p = rp->e_list.next;
 	list_del(p);
 	--rp->nevents;
-	spin_unlock_irqrestore(&mbus->lock, flags);
+	raw_spin_unlock_irqrestore(&mbus->lock, flags);
 	return list_entry(p, struct mon_event_text, e_link);
 }
 
diff --git a/drivers/usb/mon/usb_mon.h b/drivers/usb/mon/usb_mon.h
index aa64efaba366..d2a342feaad3 100644
--- a/drivers/usb/mon/usb_mon.h
+++ b/drivers/usb/mon/usb_mon.h
@@ -17,7 +17,7 @@
 
 struct mon_bus {
 	struct list_head bus_link;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	struct usb_bus *u_bus;
 
 	int text_inited;
-- 
2.43.0

Re: [PATCH] usb: mon: Make mon_bus::lock a raw spinlock

Posted by Alan Stern 2 weeks, 3 days ago

On Mon, Sep 15, 2025 at 09:29:13AM +0800, Lizhi Xu wrote:
> Interrupts are disabled before entering usb_hcd_giveback_urb().

This needs to be fixed in the usbip driver.  There is no need to change 
usbmon.

> A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
> acquired with disabled interrupts.
> 
> Make mon_bus::lock a raw spinlock so it can be used with interrupts disabled.

See commit 8d63c83d8eb9 ("USB: gadget: dummy-hcd: Fix locking bug in 
RT-enabled kernels") for an example of how to avoid disabling 
interrupts before calling usb_hcd_giveback_urb().

Alan Stern

[PATCH V2] usbip: Fix locking bug in RT-enabled kernels

Posted by Lizhi Xu 2 weeks, 2 days ago

Interrupts are disabled before entering usb_hcd_giveback_urb().
A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
acquired with disabled interrupts.

Save the interrupt status and restore it after usb_hcd_giveback_urb().

syz reported:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
Call Trace:
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:44 [inline]
 mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
 mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
 usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
 __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
 vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818

Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
V1 -> V2: fix it in usbip

 drivers/usb/usbip/vhci_hcd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index e70fba9f55d6..eb6de7e8ea7b 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -809,15 +809,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
 no_need_xmit:
 	usb_hcd_unlink_urb_from_ep(hcd, urb);
 no_need_unlink:
-	spin_unlock_irqrestore(&vhci->lock, flags);
 	if (!ret) {
 		/* usb_hcd_giveback_urb() should be called with
 		 * irqs disabled
 		 */
-		local_irq_disable();
+		spin_unlock(&vhci->lock);
 		usb_hcd_giveback_urb(hcd, urb, urb->status);
-		local_irq_enable();
+		spin_lock(&vhci->lock);
 	}
+	spin_unlock_irqrestore(&vhci->lock, flags);
 	return ret;
 }
 
-- 
2.43.0

Re: [PATCH V2] usbip: Fix locking bug in RT-enabled kernels

Posted by Alan Stern 2 weeks, 1 day ago

On Tue, Sep 16, 2025 at 09:41:43AM +0800, Lizhi Xu wrote:
> Interrupts are disabled before entering usb_hcd_giveback_urb().
> A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
> acquired with disabled interrupts.
> 
> Save the interrupt status and restore it after usb_hcd_giveback_urb().
> 
> syz reported:
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> Call Trace:
>  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>  rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
>  spin_lock include/linux/spinlock_rt.h:44 [inline]
>  mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
>  mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
>  usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
>  __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
>  vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818
> 
> Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> ---
> V1 -> V2: fix it in usbip
> 
>  drivers/usb/usbip/vhci_hcd.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> index e70fba9f55d6..eb6de7e8ea7b 100644
> --- a/drivers/usb/usbip/vhci_hcd.c
> +++ b/drivers/usb/usbip/vhci_hcd.c
> @@ -809,15 +809,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
>  no_need_xmit:
>  	usb_hcd_unlink_urb_from_ep(hcd, urb);
>  no_need_unlink:
> -	spin_unlock_irqrestore(&vhci->lock, flags);
>  	if (!ret) {
>  		/* usb_hcd_giveback_urb() should be called with
>  		 * irqs disabled
>  		 */
> -		local_irq_disable();
> +		spin_unlock(&vhci->lock);
>  		usb_hcd_giveback_urb(hcd, urb, urb->status);
> -		local_irq_enable();
> +		spin_lock(&vhci->lock);
>  	}
> +	spin_unlock_irqrestore(&vhci->lock, flags);
>  	return ret;
>  }

This looks right to me; it's the same pattern that the other host 
controller drivers use.  However, the final decision is up to the usbip 
maintainers.

Also, there are several other places in the usbip drivers where 
usb_hcd_giveback_urb() gets called; shouldn't they all be changed to 
follow this pattern?

Alan Stern

Re: [PATCH V2] usbip: Fix locking bug in RT-enabled kernels

Posted by Shuah Khan 2 weeks, 1 day ago

On 9/16/25 09:47, Alan Stern wrote:
> On Tue, Sep 16, 2025 at 09:41:43AM +0800, Lizhi Xu wrote:
>> Interrupts are disabled before entering usb_hcd_giveback_urb().
>> A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
>> acquired with disabled interrupts.
>>
>> Save the interrupt status and restore it after usb_hcd_giveback_urb().
>>
>> syz reported:
>> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
>> Call Trace:
>>   dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>>   rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
>>   spin_lock include/linux/spinlock_rt.h:44 [inline]
>>   mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
>>   mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
>>   usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
>>   __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
>>   vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818
>>
>> Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
>> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
>> ---
>> V1 -> V2: fix it in usbip
>>
>>   drivers/usb/usbip/vhci_hcd.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
>> index e70fba9f55d6..eb6de7e8ea7b 100644
>> --- a/drivers/usb/usbip/vhci_hcd.c
>> +++ b/drivers/usb/usbip/vhci_hcd.c
>> @@ -809,15 +809,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
>>   no_need_xmit:
>>   	usb_hcd_unlink_urb_from_ep(hcd, urb);
>>   no_need_unlink:
>> -	spin_unlock_irqrestore(&vhci->lock, flags);
>>   	if (!ret) {
>>   		/* usb_hcd_giveback_urb() should be called with
>>   		 * irqs disabled
>>   		 */
>> -		local_irq_disable();
>> +		spin_unlock(&vhci->lock);
>>   		usb_hcd_giveback_urb(hcd, urb, urb->status);
>> -		local_irq_enable();
>> +		spin_lock(&vhci->lock);
>>   	}
>> +	spin_unlock_irqrestore(&vhci->lock, flags);
>>   	return ret;
>>   }
> 
> This looks right to me; it's the same pattern that the other host
> controller drivers use.  However, the final decision is up to the usbip
> maintainers.
> 
> Also, there are several other places in the usbip drivers where
> usb_hcd_giveback_urb() gets called; shouldn't they all be changed to
> follow this pattern?
> 

Looks good to me.
+1 on changing all other instances - can we do that?

thanks,
-- Shuah

Re: [PATCH V2] usbip: Fix locking bug in RT-enabled kernels

Posted by Lizhi Xu 2 weeks, 1 day ago

On Tue, 16 Sep 2025 17:33:44 -0600, Shuah Khan wrote:
>On 9/16/25 09:47, Alan Stern wrote:
>> On Tue, Sep 16, 2025 at 09:41:43AM +0800, Lizhi Xu wrote:
>>> Interrupts are disabled before entering usb_hcd_giveback_urb().
>>> A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
>>> acquired with disabled interrupts.
>>>
>>> Save the interrupt status and restore it after usb_hcd_giveback_urb().
>>>
>>> syz reported:
>>> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
>>> Call Trace:
>>>   dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>>>   rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
>>>   spin_lock include/linux/spinlock_rt.h:44 [inline]
>>>   mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
>>>   mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
>>>   usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
>>>   __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
>>>   vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818
>>>
>>> Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
>>> Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
>>> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
>>> ---
>>> V1 -> V2: fix it in usbip
>>>
>>>   drivers/usb/usbip/vhci_hcd.c | 6 +++---
>>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
>>> index e70fba9f55d6..eb6de7e8ea7b 100644
>>> --- a/drivers/usb/usbip/vhci_hcd.c
>>> +++ b/drivers/usb/usbip/vhci_hcd.c
>>> @@ -809,15 +809,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
>>>   no_need_xmit:
>>>   	usb_hcd_unlink_urb_from_ep(hcd, urb);
>>>   no_need_unlink:
>>> -	spin_unlock_irqrestore(&vhci->lock, flags);
>>>   	if (!ret) {
>>>   		/* usb_hcd_giveback_urb() should be called with
>>>   		 * irqs disabled
>>>   		 */
>>> -		local_irq_disable();
>>> +		spin_unlock(&vhci->lock);
>>>   		usb_hcd_giveback_urb(hcd, urb, urb->status);
>>> -		local_irq_enable();
>>> +		spin_lock(&vhci->lock);
>>>   	}
>>> +	spin_unlock_irqrestore(&vhci->lock, flags);
>>>   	return ret;
>>>   }
>>
>> This looks right to me; it's the same pattern that the other host
>> controller drivers use.  However, the final decision is up to the usbip
>> maintainers.
>>
>> Also, there are several other places in the usbip drivers where
>> usb_hcd_giveback_urb() gets called; shouldn't they all be changed to
>> follow this pattern?
>>
>
>Looks good to me.
>+1 on changing all other instances - can we do that?
I'm replying to both of you. Personally, I suggest this isn't necessary
right now; it's safer to wait until a problem is reported before fixing it.

Also, the context of several other calls to usb_hcd_giveback_urb() in usbip
differs from the current issue. Enabling RT_PREEMPT shouldn't cause similar
issues.

BR,
Lizhi

Re: [PATCH V2] usbip: Fix locking bug in RT-enabled kernels

Posted by Shuah Khan 2 weeks ago

On 9/16/25 18:51, Lizhi Xu wrote:
> On Tue, 16 Sep 2025 17:33:44 -0600, Shuah Khan wrote:
>> On 9/16/25 09:47, Alan Stern wrote:
>>> On Tue, Sep 16, 2025 at 09:41:43AM +0800, Lizhi Xu wrote:
>>>> Interrupts are disabled before entering usb_hcd_giveback_urb().
>>>> A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
>>>> acquired with disabled interrupts.
>>>>
>>>> Save the interrupt status and restore it after usb_hcd_giveback_urb().
>>>>
>>>> syz reported:
>>>> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
>>>> Call Trace:
>>>>    dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>>>>    rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
>>>>    spin_lock include/linux/spinlock_rt.h:44 [inline]
>>>>    mon_bus_complete drivers/usb/mon/mon_main.c:134 [inline]
>>>>    mon_complete+0x5c/0x200 drivers/usb/mon/mon_main.c:147
>>>>    usbmon_urb_complete include/linux/usb/hcd.h:738 [inline]
>>>>    __usb_hcd_giveback_urb+0x254/0x5e0 drivers/usb/core/hcd.c:1647
>>>>    vhci_urb_enqueue+0xb4f/0xe70 drivers/usb/usbip/vhci_hcd.c:818
>>>>
>>>> Reported-by: syzbot+205ef33a3b636b4181fb@syzkaller.appspotmail.com
>>>> Closes: https://syzkaller.appspot.com/bug?extid=205ef33a3b636b4181fb
>>>> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
>>>> ---
>>>> V1 -> V2: fix it in usbip
>>>>
>>>>    drivers/usb/usbip/vhci_hcd.c | 6 +++---
>>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
>>>> index e70fba9f55d6..eb6de7e8ea7b 100644
>>>> --- a/drivers/usb/usbip/vhci_hcd.c
>>>> +++ b/drivers/usb/usbip/vhci_hcd.c
>>>> @@ -809,15 +809,15 @@ static int vhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
>>>>    no_need_xmit:
>>>>    	usb_hcd_unlink_urb_from_ep(hcd, urb);
>>>>    no_need_unlink:
>>>> -	spin_unlock_irqrestore(&vhci->lock, flags);
>>>>    	if (!ret) {
>>>>    		/* usb_hcd_giveback_urb() should be called with
>>>>    		 * irqs disabled
>>>>    		 */
>>>> -		local_irq_disable();
>>>> +		spin_unlock(&vhci->lock);
>>>>    		usb_hcd_giveback_urb(hcd, urb, urb->status);
>>>> -		local_irq_enable();
>>>> +		spin_lock(&vhci->lock);
>>>>    	}
>>>> +	spin_unlock_irqrestore(&vhci->lock, flags);
>>>>    	return ret;
>>>>    }
>>>
>>> This looks right to me; it's the same pattern that the other host
>>> controller drivers use.  However, the final decision is up to the usbip
>>> maintainers.
>>>
>>> Also, there are several other places in the usbip drivers where
>>> usb_hcd_giveback_urb() gets called; shouldn't they all be changed to
>>> follow this pattern?
>>>
>>
>> Looks good to me.
>> +1 on changing all other instances - can we do that?
> I'm replying to both of you. Personally, I suggest this isn't necessary
> right now; it's safer to wait until a problem is reported before fixing it.
> 
> Also, the context of several other calls to usb_hcd_giveback_urb() in usbip
> differs from the current issue. Enabling RT_PREEMPT shouldn't cause similar
> issues.

Fair enough reasoning to wait. Here is my Acked by.

Acked-by: Shuah Khan <skhan@linuxfoundation.org>

Greg, please pick this up.

thanks,
-- Shuah