[PATCH 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

[PATCH 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

[Jeffy Chen]

It looks like bnep_session has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
---

 net/bluetooth/bnep/core.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index fbf251f..da04d51 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -484,16 +484,16 @@ static int bnep_session(void *arg)
 	struct net_device *dev = s->dev;
 	struct sock *sk = s->sock->sk;
 	struct sk_buff *skb;
-	wait_queue_t wait;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
 	BT_DBG("");
 
 	set_user_nice(current, -15);
 
-	init_waitqueue_entry(&wait, current);
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 
 		if (atomic_read(&s->terminate))
 			break;
@@ -515,9 +515,8 @@ static int bnep_session(void *arg)
 				break;
 		netif_wake_queue(dev);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(sk_sleep(sk), &wait);
 
 	/* Cleanup session */
@@ -666,7 +665,11 @@ int bnep_del_connection(struct bnep_conndel_req *req)
 	s = __bnep_get_session(req->dst);
 	if (s) {
 		atomic_inc(&s->terminate);
-		wake_up_process(s->task);
+
+		/* Ensure session->terminate is updated */
+		smp_mb__after_atomic();
+
+		wake_up_interruptible(sk_sleep(s->sock->sk));
 	} else
 		err = -ENOENT;
 
-- 
2.1.4

[PATCH 2/3] Bluetooth: cmtp: fix possible might sleep error in cmtp_session

[Jeffy Chen]

It looks like cmtp_session has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
---

 net/bluetooth/cmtp/core.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
index 9e59b66..6b03f2b 100644
--- a/net/bluetooth/cmtp/core.c
+++ b/net/bluetooth/cmtp/core.c
@@ -280,16 +280,16 @@ static int cmtp_session(void *arg)
 	struct cmtp_session *session = arg;
 	struct sock *sk = session->sock->sk;
 	struct sk_buff *skb;
-	wait_queue_t wait;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
 	BT_DBG("session %p", session);
 
 	set_user_nice(current, -15);
 
-	init_waitqueue_entry(&wait, current);
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 
 		if (atomic_read(&session->terminate))
 			break;
@@ -306,9 +306,8 @@ static int cmtp_session(void *arg)
 
 		cmtp_process_transmit(session);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(sk_sleep(sk), &wait);
 
 	down_write(&cmtp_session_sem);
@@ -393,7 +392,11 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock)
 		err = cmtp_attach_device(session);
 		if (err < 0) {
 			atomic_inc(&session->terminate);
-			wake_up_process(session->task);
+
+			/* Ensure session->terminate is updated */
+			smp_mb__after_atomic();
+
+			wake_up_interruptible(sk_sleep(session->sock->sk));
 			up_write(&cmtp_session_sem);
 			return err;
 		}
@@ -431,7 +434,11 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
 
 		/* Stop session thread */
 		atomic_inc(&session->terminate);
-		wake_up_process(session->task);
+
+		/* Ensure session->terminate is updated */
+		smp_mb__after_atomic();
+
+		wake_up_interruptible(sk_sleep(session->sock->sk));
 	} else
 		err = -ENOENT;
 
-- 
2.1.4

Re: [PATCH 2/3] Bluetooth: cmtp: fix possible might sleep error in cmtp_session

[Brian Norris]

Hi,

On Tue, Jan 24, 2017 at 12:07:50PM +0800, Jeffy Chen wrote:
> It looks like cmtp_session has same pattern as the issue reported in
> old rfcomm:
> 
> 	while (1) {
> 		set_current_state(TASK_INTERRUPTIBLE);
> 		if (condition)
> 			break;
> 		// may call might_sleep here
> 		schedule();
> 	}
> 	__set_current_state(TASK_RUNNING);
> 
> Which fixed at:
> 	dfb2fae Bluetooth: Fix nested sleeps
> 
> So let's fix it at the same way, also follow the suggestion of:
> https://lwn.net/Articles/628628/
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> ---
> 
>  net/bluetooth/cmtp/core.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
> index 9e59b66..6b03f2b 100644
> --- a/net/bluetooth/cmtp/core.c
> +++ b/net/bluetooth/cmtp/core.c
> @@ -280,16 +280,16 @@ static int cmtp_session(void *arg)
>  	struct cmtp_session *session = arg;
>  	struct sock *sk = session->sock->sk;
>  	struct sk_buff *skb;
> -	wait_queue_t wait;
> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>  
>  	BT_DBG("session %p", session);
>  
>  	set_user_nice(current, -15);
>  
> -	init_waitqueue_entry(&wait, current);
>  	add_wait_queue(sk_sleep(sk), &wait);
>  	while (1) {
> -		set_current_state(TASK_INTERRUPTIBLE);
> +		/* Ensure session->terminate is updated */
> +		smp_mb__before_atomic();
>  
>  		if (atomic_read(&session->terminate))
>  			break;
> @@ -306,9 +306,8 @@ static int cmtp_session(void *arg)
>  
>  		cmtp_process_transmit(session);
>  
> -		schedule();
> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
>  	}
> -	__set_current_state(TASK_RUNNING);
>  	remove_wait_queue(sk_sleep(sk), &wait);
>  
>  	down_write(&cmtp_session_sem);
> @@ -393,7 +392,11 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock)
>  		err = cmtp_attach_device(session);
>  		if (err < 0) {
>  			atomic_inc(&session->terminate);
> -			wake_up_process(session->task);
> +
> +			/* Ensure session->terminate is updated */
> +			smp_mb__after_atomic();
> +

Same comment about the barrier.

> +			wake_up_interruptible(sk_sleep(session->sock->sk));
>  			up_write(&cmtp_session_sem);
>  			return err;
>  		}
> @@ -431,7 +434,11 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
>  
>  		/* Stop session thread */
>  		atomic_inc(&session->terminate);
> -		wake_up_process(session->task);
> +
> +		/* Ensure session->terminate is updated */
> +		smp_mb__after_atomic();

And again.

But otherwise I think this looks OK, again with the caveat that I don't
know Bluetooth/CMTP that well:

Reviewed-by: Brian Norris <briannorris@chromium.org>

> +
> +		wake_up_interruptible(sk_sleep(session->sock->sk));
>  	} else
>  		err = -ENOENT;
>  
> -- 
> 2.1.4
> 
> 

Re: [PATCH 2/3] Bluetooth: cmtp: fix possible might sleep error in cmtp_session

[jeffy]

Hi brian,

On 02/11/2017 09:43 AM, Brian Norris wrote:
> Hi,
>
> On Tue, Jan 24, 2017 at 12:07:50PM +0800, Jeffy Chen wrote:
>> It looks like cmtp_session has same pattern as the issue reported in
>> old rfcomm:
>>
>> 	while (1) {
>> 		set_current_state(TASK_INTERRUPTIBLE);
>> 		if (condition)
>> 			break;
>> 		// may call might_sleep here
>> 		schedule();
>> 	}
>> 	__set_current_state(TASK_RUNNING);
>>
>> Which fixed at:
>> 	dfb2fae Bluetooth: Fix nested sleeps
>>
>> So let's fix it at the same way, also follow the suggestion of:
>> https://lwn.net/Articles/628628/
>>
>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>> ---
>>
>>   net/bluetooth/cmtp/core.c | 21 ++++++++++++++-------
>>   1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/net/bluetooth/cmtp/core.c b/net/bluetooth/cmtp/core.c
>> index 9e59b66..6b03f2b 100644
>> --- a/net/bluetooth/cmtp/core.c
>> +++ b/net/bluetooth/cmtp/core.c
>> @@ -280,16 +280,16 @@ static int cmtp_session(void *arg)
>>   	struct cmtp_session *session = arg;
>>   	struct sock *sk = session->sock->sk;
>>   	struct sk_buff *skb;
>> -	wait_queue_t wait;
>> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>>   
>>   	BT_DBG("session %p", session);
>>   
>>   	set_user_nice(current, -15);
>>   
>> -	init_waitqueue_entry(&wait, current);
>>   	add_wait_queue(sk_sleep(sk), &wait);
>>   	while (1) {
>> -		set_current_state(TASK_INTERRUPTIBLE);
>> +		/* Ensure session->terminate is updated */
>> +		smp_mb__before_atomic();
>>   
>>   		if (atomic_read(&session->terminate))
>>   			break;
>> @@ -306,9 +306,8 @@ static int cmtp_session(void *arg)
>>   
>>   		cmtp_process_transmit(session);
>>   
>> -		schedule();
>> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
>>   	}
>> -	__set_current_state(TASK_RUNNING);
>>   	remove_wait_queue(sk_sleep(sk), &wait);
>>   
>>   	down_write(&cmtp_session_sem);
>> @@ -393,7 +392,11 @@ int cmtp_add_connection(struct cmtp_connadd_req *req, struct socket *sock)
>>   		err = cmtp_attach_device(session);
>>   		if (err < 0) {
>>   			atomic_inc(&session->terminate);
>> -			wake_up_process(session->task);
>> +
>> +			/* Ensure session->terminate is updated */
>> +			smp_mb__after_atomic();
>> +
> Same comment about the barrier.
Done, there are barriers in wake functions indeed, thanx!
>
>> +			wake_up_interruptible(sk_sleep(session->sock->sk));
>>   			up_write(&cmtp_session_sem);
>>   			return err;
>>   		}
>> @@ -431,7 +434,11 @@ int cmtp_del_connection(struct cmtp_conndel_req *req)
>>   
>>   		/* Stop session thread */
>>   		atomic_inc(&session->terminate);
>> -		wake_up_process(session->task);
>> +
>> +		/* Ensure session->terminate is updated */
>> +		smp_mb__after_atomic();
> And again.
>
> But otherwise I think this looks OK, again with the caveat that I don't
> know Bluetooth/CMTP that well:
>
> Reviewed-by: Brian Norris <briannorris@chromium.org>
>
>> +
>> +		wake_up_interruptible(sk_sleep(session->sock->sk));
>>   	} else
>>   		err = -ENOENT;
>>   
>> -- 
>> 2.1.4
>>
>>
>
>

[PATCH 3/3] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread

[Jeffy Chen]

It looks like hidp_session_thread has same pattern as the issue reported in
old rfcomm:

	while (1) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (condition)
			break;
		// may call might_sleep here
		schedule();
	}
	__set_current_state(TASK_RUNNING);

Which fixed at:
	dfb2fae Bluetooth: Fix nested sleeps

So let's fix it at the same way, also follow the suggestion of:
https://lwn.net/Articles/628628/

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
---

 net/bluetooth/hidp/core.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..43d6e6a 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -36,6 +36,7 @@
 #define VERSION "1.2"
 
 static DECLARE_RWSEM(hidp_session_sem);
+static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
 static LIST_HEAD(hidp_session_list);
 
 static unsigned char hidp_keycode[256] = {
@@ -1068,12 +1069,15 @@ static int hidp_session_start_sync(struct hidp_session *session)
  * Wake up session thread and notify it to stop. This is asynchronous and
  * returns immediately. Call this whenever a runtime error occurs and you want
  * the session to stop.
- * Note: wake_up_process() performs any necessary memory-barriers for us.
  */
 static void hidp_session_terminate(struct hidp_session *session)
 {
 	atomic_inc(&session->terminate);
-	wake_up_process(session->task);
+
+	/* Ensure session->terminate is updated */
+	smp_mb__after_atomic();
+
+	wake_up_interruptible(&hidp_session_wq);
 }
 
 /*
@@ -1180,7 +1184,9 @@ static void hidp_session_run(struct hidp_session *session)
 	struct sock *ctrl_sk = session->ctrl_sock->sk;
 	struct sock *intr_sk = session->intr_sock->sk;
 	struct sk_buff *skb;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+	add_wait_queue(&hidp_session_wq, &wait);
 	for (;;) {
 		/*
 		 * This thread can be woken up two ways:
@@ -1188,12 +1194,10 @@ static void hidp_session_run(struct hidp_session *session)
 		 *    session->terminate flag and wakes this thread up.
 		 *  - Via modifying the socket state of ctrl/intr_sock. This
 		 *    thread is woken up by ->sk_state_changed().
-		 *
-		 * Note: set_current_state() performs any necessary
-		 * memory-barriers for us.
 		 */
-		set_current_state(TASK_INTERRUPTIBLE);
 
+		/* Ensure session->terminate is updated */
+		smp_mb__before_atomic();
 		if (atomic_read(&session->terminate))
 			break;
 
@@ -1227,11 +1231,14 @@ static void hidp_session_run(struct hidp_session *session)
 		hidp_process_transmit(session, &session->ctrl_transmit,
 				      session->ctrl_sock);
 
-		schedule();
+		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
+	remove_wait_queue(&hidp_session_wq, &wait);
 
 	atomic_inc(&session->terminate);
-	set_current_state(TASK_RUNNING);
+
+	/* Ensure session->terminate is updated */
+	smp_mb__after_atomic();
 }
 
 /*
-- 
2.1.4

Re: [PATCH 3/3] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread

[Brian Norris]

Hi Jeffy,

I'm really not an expert on bluetooth or HIDP, but I can't bring myself
to say that this is correct. I still think you have a problem.

On Tue, Jan 24, 2017 at 12:07:51PM +0800, Jeffy Chen wrote:
> It looks like hidp_session_thread has same pattern as the issue reported in
> old rfcomm:
> 
> 	while (1) {
> 		set_current_state(TASK_INTERRUPTIBLE);
> 		if (condition)
> 			break;
> 		// may call might_sleep here
> 		schedule();
> 	}
> 	__set_current_state(TASK_RUNNING);
> 
> Which fixed at:
> 	dfb2fae Bluetooth: Fix nested sleeps
> 
> So let's fix it at the same way, also follow the suggestion of:
> https://lwn.net/Articles/628628/
> 
> Signed-off-by: Jeffy Chen <jeffy.chen-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> ---
> 
>  net/bluetooth/hidp/core.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> index 0bec458..43d6e6a 100644
> --- a/net/bluetooth/hidp/core.c
> +++ b/net/bluetooth/hidp/core.c
> @@ -36,6 +36,7 @@
>  #define VERSION "1.2"
>  
>  static DECLARE_RWSEM(hidp_session_sem);
> +static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
>  static LIST_HEAD(hidp_session_list);
>  
>  static unsigned char hidp_keycode[256] = {
> @@ -1068,12 +1069,15 @@ static int hidp_session_start_sync(struct hidp_session *session)
>   * Wake up session thread and notify it to stop. This is asynchronous and
>   * returns immediately. Call this whenever a runtime error occurs and you want
>   * the session to stop.
> - * Note: wake_up_process() performs any necessary memory-barriers for us.
>   */
>  static void hidp_session_terminate(struct hidp_session *session)
>  {
>  	atomic_inc(&session->terminate);
> -	wake_up_process(session->task);
> +
> +	/* Ensure session->terminate is updated */
> +	smp_mb__after_atomic();
> +
> +	wake_up_interruptible(&hidp_session_wq);

So, you're adding a whole new wait queue here.

>  }
>  
>  /*
> @@ -1180,7 +1184,9 @@ static void hidp_session_run(struct hidp_session *session)
>  	struct sock *ctrl_sk = session->ctrl_sock->sk;
>  	struct sock *intr_sk = session->intr_sock->sk;
>  	struct sk_buff *skb;
> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>  
> +	add_wait_queue(&hidp_session_wq, &wait);
>  	for (;;) {
>  		/*
>  		 * This thread can be woken up two ways:
> @@ -1188,12 +1194,10 @@ static void hidp_session_run(struct hidp_session *session)
>  		 *    session->terminate flag and wakes this thread up.
>  		 *  - Via modifying the socket state of ctrl/intr_sock. This
>  		 *    thread is woken up by ->sk_state_changed().
> -		 *
> -		 * Note: set_current_state() performs any necessary
> -		 * memory-barriers for us.
>  		 */
> -		set_current_state(TASK_INTERRUPTIBLE);
>  
> +		/* Ensure session->terminate is updated */
> +		smp_mb__before_atomic();
>  		if (atomic_read(&session->terminate))
>  			break;
>  
> @@ -1227,11 +1231,14 @@ static void hidp_session_run(struct hidp_session *session)
>  		hidp_process_transmit(session, &session->ctrl_transmit,
>  				      session->ctrl_sock);
>  
> -		schedule();
> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);

And you're waiting on it here.

But you're already on two other wait queues (hidp_session_thread()). So
the nice WQ_FLAG_WOKEN handling will only happen if you get woken via
the new hidp_session_wq queue. But what about the other two? Seems like
again you might have a race condition that would lead you to
(temporarily, at least?) missing a wake-up attempt.

I'm not really sure what the best way to resolve this would be. My best
guess would be to either consolidate the use of these wait queues, or
lese roll a version of wait_woken() to handle 2 or more wait heads...

Am I wrong? I easily could be.

Brian

>  	}
> +	remove_wait_queue(&hidp_session_wq, &wait);
>  
>  	atomic_inc(&session->terminate);
> -	set_current_state(TASK_RUNNING);
> +
> +	/* Ensure session->terminate is updated */
> +	smp_mb__after_atomic();
>  }
>  
>  /*
> -- 
> 2.1.4
> 
> 

Re: [PATCH 3/3] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread

[jeffy]

Hi brian,

On 02/11/2017 09:26 AM, Brian Norris wrote:
> Hi Jeffy,
>
> I'm really not an expert on bluetooth or HIDP, but I can't bring myself
> to say that this is correct. I still think you have a problem.
>
> On Tue, Jan 24, 2017 at 12:07:51PM +0800, Jeffy Chen wrote:
>> It looks like hidp_session_thread has same pattern as the issue reported in
>> old rfcomm:
>>
>> 	while (1) {
>> 		set_current_state(TASK_INTERRUPTIBLE);
>> 		if (condition)
>> 			break;
>> 		// may call might_sleep here
>> 		schedule();
>> 	}
>> 	__set_current_state(TASK_RUNNING);
>>
>> Which fixed at:
>> 	dfb2fae Bluetooth: Fix nested sleeps
>>
>> So let's fix it at the same way, also follow the suggestion of:
>> https://lwn.net/Articles/628628/
>>
>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>> ---
>>
>>   net/bluetooth/hidp/core.c | 23 +++++++++++++++--------
>>   1 file changed, 15 insertions(+), 8 deletions(-)
>>
>> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
>> index 0bec458..43d6e6a 100644
>> --- a/net/bluetooth/hidp/core.c
>> +++ b/net/bluetooth/hidp/core.c
>> @@ -36,6 +36,7 @@
>>   #define VERSION "1.2"
>>   
>>   static DECLARE_RWSEM(hidp_session_sem);
>> +static DECLARE_WAIT_QUEUE_HEAD(hidp_session_wq);
>>   static LIST_HEAD(hidp_session_list);
>>   
>>   static unsigned char hidp_keycode[256] = {
>> @@ -1068,12 +1069,15 @@ static int hidp_session_start_sync(struct hidp_session *session)
>>    * Wake up session thread and notify it to stop. This is asynchronous and
>>    * returns immediately. Call this whenever a runtime error occurs and you want
>>    * the session to stop.
>> - * Note: wake_up_process() performs any necessary memory-barriers for us.
>>    */
>>   static void hidp_session_terminate(struct hidp_session *session)
>>   {
>>   	atomic_inc(&session->terminate);
>> -	wake_up_process(session->task);
>> +
>> +	/* Ensure session->terminate is updated */
>> +	smp_mb__after_atomic();
>> +
>> +	wake_up_interruptible(&hidp_session_wq);
> So, you're adding a whole new wait queue here.
>
>>   }
>>   
>>   /*
>> @@ -1180,7 +1184,9 @@ static void hidp_session_run(struct hidp_session *session)
>>   	struct sock *ctrl_sk = session->ctrl_sock->sk;
>>   	struct sock *intr_sk = session->intr_sock->sk;
>>   	struct sk_buff *skb;
>> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>>   
>> +	add_wait_queue(&hidp_session_wq, &wait);
>>   	for (;;) {
>>   		/*
>>   		 * This thread can be woken up two ways:
>> @@ -1188,12 +1194,10 @@ static void hidp_session_run(struct hidp_session *session)
>>   		 *    session->terminate flag and wakes this thread up.
>>   		 *  - Via modifying the socket state of ctrl/intr_sock. This
>>   		 *    thread is woken up by ->sk_state_changed().
>> -		 *
>> -		 * Note: set_current_state() performs any necessary
>> -		 * memory-barriers for us.
>>   		 */
>> -		set_current_state(TASK_INTERRUPTIBLE);
>>   
>> +		/* Ensure session->terminate is updated */
>> +		smp_mb__before_atomic();
>>   		if (atomic_read(&session->terminate))
>>   			break;
>>   
>> @@ -1227,11 +1231,14 @@ static void hidp_session_run(struct hidp_session *session)
>>   		hidp_process_transmit(session, &session->ctrl_transmit,
>>   				      session->ctrl_sock);
>>   
>> -		schedule();
>> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
> And you're waiting on it here.
>
> But you're already on two other wait queues (hidp_session_thread()). So
> the nice WQ_FLAG_WOKEN handling will only happen if you get woken via
> the new hidp_session_wq queue. But what about the other two? Seems like
> again you might have a race condition that would lead you to
> (temporarily, at least?) missing a wake-up attempt.
Thanx for point that out.
>
> I'm not really sure what the best way to resolve this would be. My best
> guess would be to either consolidate the use of these wait queues, or
> lese roll a version of wait_woken() to handle 2 or more wait heads...
>
> Am I wrong? I easily could be.
>
> Brian
>
>>   	}
>> +	remove_wait_queue(&hidp_session_wq, &wait);
>>   
>>   	atomic_inc(&session->terminate);
>> -	set_current_state(TASK_RUNNING);
>> +
>> +	/* Ensure session->terminate is updated */
>> +	smp_mb__after_atomic();
>>   }
>>   
>>   /*
>> -- 
>> 2.1.4
>>
>>
>
>

Re: [PATCH 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

[Brian Norris]

Hi,

On Tue, Jan 24, 2017 at 12:07:49PM +0800, Jeffy Chen wrote:
> It looks like bnep_session has same pattern as the issue reported in
> old rfcomm:
> 
> 	while (1) {
> 		set_current_state(TASK_INTERRUPTIBLE);
> 		if (condition)
> 			break;
> 		// may call might_sleep here
> 		schedule();
> 	}
> 	__set_current_state(TASK_RUNNING);
> 
> Which fixed at:
> 	dfb2fae Bluetooth: Fix nested sleeps
> 
> So let's fix it at the same way, also follow the suggestion of:
> https://lwn.net/Articles/628628/
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> ---
> 
>  net/bluetooth/bnep/core.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
> index fbf251f..da04d51 100644
> --- a/net/bluetooth/bnep/core.c
> +++ b/net/bluetooth/bnep/core.c
> @@ -484,16 +484,16 @@ static int bnep_session(void *arg)
>  	struct net_device *dev = s->dev;
>  	struct sock *sk = s->sock->sk;
>  	struct sk_buff *skb;
> -	wait_queue_t wait;
> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>  
>  	BT_DBG("");
>  
>  	set_user_nice(current, -15);
>  
> -	init_waitqueue_entry(&wait, current);
>  	add_wait_queue(sk_sleep(sk), &wait);
>  	while (1) {
> -		set_current_state(TASK_INTERRUPTIBLE);
> +		/* Ensure session->terminate is updated */
> +		smp_mb__before_atomic();
>  
>  		if (atomic_read(&s->terminate))
>  			break;
> @@ -515,9 +515,8 @@ static int bnep_session(void *arg)
>  				break;
>  		netif_wake_queue(dev);
>  
> -		schedule();
> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
>  	}
> -	__set_current_state(TASK_RUNNING);
>  	remove_wait_queue(sk_sleep(sk), &wait);
>  
>  	/* Cleanup session */
> @@ -666,7 +665,11 @@ int bnep_del_connection(struct bnep_conndel_req *req)
>  	s = __bnep_get_session(req->dst);
>  	if (s) {
>  		atomic_inc(&s->terminate);
> -		wake_up_process(s->task);
> +
> +		/* Ensure session->terminate is updated */
> +		smp_mb__after_atomic();
> +

__wake_up() suggests:

 * It may be assumed that this function implies a write memory barrier before
 * changing the task state if and only if any tasks are woken up.

so the above barrier is probably unnecessary. I'm not so sure about the
one before atomic_read(); seems fine.

Other than that, I this looks ok:

Reviewed-by: Brian Norris <briannorris@chromium.or>

But I haven't been testing BNEP.

Brian

> +		wake_up_interruptible(sk_sleep(s->sock->sk));
>  	} else
>  		err = -ENOENT;
>  
> -- 
> 2.1.4
> 
> 

Re: [PATCH 1/3] Bluetooth: bnep: fix possible might sleep error in bnep_session

[jeffy]

Hi brian,

On 02/11/2017 09:40 AM, Brian Norris wrote:
> Hi,
>
> On Tue, Jan 24, 2017 at 12:07:49PM +0800, Jeffy Chen wrote:
>> It looks like bnep_session has same pattern as the issue reported in
>> old rfcomm:
>>
>> 	while (1) {
>> 		set_current_state(TASK_INTERRUPTIBLE);
>> 		if (condition)
>> 			break;
>> 		// may call might_sleep here
>> 		schedule();
>> 	}
>> 	__set_current_state(TASK_RUNNING);
>>
>> Which fixed at:
>> 	dfb2fae Bluetooth: Fix nested sleeps
>>
>> So let's fix it at the same way, also follow the suggestion of:
>> https://lwn.net/Articles/628628/
>>
>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>> ---
>>
>>   net/bluetooth/bnep/core.c | 15 +++++++++------
>>   1 file changed, 9 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
>> index fbf251f..da04d51 100644
>> --- a/net/bluetooth/bnep/core.c
>> +++ b/net/bluetooth/bnep/core.c
>> @@ -484,16 +484,16 @@ static int bnep_session(void *arg)
>>   	struct net_device *dev = s->dev;
>>   	struct sock *sk = s->sock->sk;
>>   	struct sk_buff *skb;
>> -	wait_queue_t wait;
>> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>>   
>>   	BT_DBG("");
>>   
>>   	set_user_nice(current, -15);
>>   
>> -	init_waitqueue_entry(&wait, current);
>>   	add_wait_queue(sk_sleep(sk), &wait);
>>   	while (1) {
>> -		set_current_state(TASK_INTERRUPTIBLE);
>> +		/* Ensure session->terminate is updated */
>> +		smp_mb__before_atomic();
>>   
>>   		if (atomic_read(&s->terminate))
>>   			break;
>> @@ -515,9 +515,8 @@ static int bnep_session(void *arg)
>>   				break;
>>   		netif_wake_queue(dev);
>>   
>> -		schedule();
>> +		wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
>>   	}
>> -	__set_current_state(TASK_RUNNING);
>>   	remove_wait_queue(sk_sleep(sk), &wait);
>>   
>>   	/* Cleanup session */
>> @@ -666,7 +665,11 @@ int bnep_del_connection(struct bnep_conndel_req *req)
>>   	s = __bnep_get_session(req->dst);
>>   	if (s) {
>>   		atomic_inc(&s->terminate);
>> -		wake_up_process(s->task);
>> +
>> +		/* Ensure session->terminate is updated */
>> +		smp_mb__after_atomic();
>> +
> __wake_up() suggests:
>
>   * It may be assumed that this function implies a write memory barrier before
>   * changing the task state if and only if any tasks are woken up.
>
> so the above barrier is probably unnecessary. I'm not so sure about the
> one before atomic_read(); seems fine.
Got it, thanx!
>
> Other than that, I this looks ok:
>
> Reviewed-by: Brian Norris <briannorris@chromium.or>
>
> But I haven't been testing BNEP.
>
> Brian
>
>> +		wake_up_interruptible(sk_sleep(s->sock->sk));
>>   	} else
>>   		err = -ENOENT;
>>   
>> -- 
>> 2.1.4
>>
>>
>
>